151
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Magnetic thin-film insulator with ultra-low spin wave damping for coherent nanomagnonics. Sci Rep 2014; 4:6848. [PMID: 25355200 PMCID: PMC4213793 DOI: 10.1038/srep06848] [Citation(s) in RCA: 151] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 10/03/2014] [Indexed: 11/18/2022] Open
Abstract
Wave control in the solid state has opened new avenues in modern information technology. Surface-acoustic-wave-based devices are found as mass market products in 100 millions of cellular phones. Spin waves (magnons) would offer a boost in today's data handling and security implementations, i.e., image processing and speech recognition. However, nanomagnonic devices realized so far suffer from the relatively short damping length in the metallic ferromagnets amounting to a few 10 micrometers typically. Here we demonstrate that nm-thick YIG films overcome the damping chasm. Using a conventional coplanar waveguide we excite a large series of short-wavelength spin waves (SWs). From the data we estimate a macroscopic of damping length of about 600 micrometers. The intrinsic damping parameter suggests even a record value about 1 mm allowing for magnonics-based nanotechnology with ultra-low damping. In addition, SWs at large wave vector are found to exhibit the non-reciprocal properties relevant for new concepts in nanoscale SW-based logics. We expect our results to provide the basis for coherent data processing with SWs at GHz rates and in large arrays of cellular magnetic arrays, thereby boosting the envisioned image processing and speech recognition.
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152
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Schlickeiser F, Ritzmann U, Hinzke D, Nowak U. Role of entropy in domain wall motion in thermal gradients. PHYSICAL REVIEW LETTERS 2014; 113:097201. [PMID: 25216002 DOI: 10.1103/physrevlett.113.097201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Indexed: 06/03/2023]
Abstract
Thermally driven domain wall (DW) motion caused solely by magnonic spin currents was forecast theoretically and has been measured recently in a magnetic insulator using magneto-optical Kerr effect microscopy. We present an analytical calculation of the DW velocity as well as the Walker breakdown within the framework of the Landau Lifshitz Bloch equation of motion. The temperature gradient leads to a torque term acting on the magnetization where the DW is mainly driven by the temperature dependence of the exchange stiffness, or--in a more general picture--by the maximization of entropy. The existence of this entropic torque term does not rest on the angular momentum transfer from the magnonic spin current. Hence, even DWs in antiferromagnets or compensated ferrimagnets should move accordingly. We further argue that the entropic torque exceeds that of the magnonic spin current.
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Affiliation(s)
- F Schlickeiser
- Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany
| | - U Ritzmann
- Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany
| | - D Hinzke
- Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany
| | - U Nowak
- Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany
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153
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Uchida K, Ishida M, Kikkawa T, Kirihara A, Murakami T, Saitoh E. Longitudinal spin Seebeck effect: from fundamentals to applications. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:343202. [PMID: 25105889 DOI: 10.1088/0953-8984/26/34/343202] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The spin Seebeck effect refers to the generation of spin voltage as a result of a temperature gradient in ferromagnetic or ferrimagnetic materials. When a conductor is attached to a magnet under a temperature gradient, the thermally generated spin voltage in the magnet injects a spin current into the conductor, which in turn produces electric voltage owing to the spin-orbit interaction. The spin Seebeck effect is of increasing importance in spintronics, since it enables direct generation of a spin current from heat and appears in a variety of magnets ranging from metals and semiconductors to insulators. Recent studies on the spin Seebeck effect have been conducted mainly in paramagnetic metal/ferrimagnetic insulator junction systems in the longitudinal configuration in which a spin current flowing parallel to the temperature gradient is measured. This 'longitudinal spin Seebeck effect' (LSSE) has been observed in various sample systems and exclusively established by separating the spin-current contribution from extrinsic artefacts, such as conventional thermoelectric and magnetic proximity effects. The LSSE in insulators also provides a novel and versatile pathway to thermoelectric generation in combination of the inverse spin-Hall effects. In this paper, we review basic experiments on the LSSE and discuss its potential thermoelectric applications with several demonstrations.
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Affiliation(s)
- K Uchida
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan. PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan
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154
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Tabuchi Y, Ishino S, Ishikawa T, Yamazaki R, Usami K, Nakamura Y. Hybridizing ferromagnetic magnons and microwave photons in the quantum limit. PHYSICAL REVIEW LETTERS 2014; 113:083603. [PMID: 25192098 DOI: 10.1103/physrevlett.113.083603] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Indexed: 05/23/2023]
Abstract
We demonstrate large normal-mode splitting between a magnetostatic mode (the Kittel mode) in a ferromagnetic sphere of yttrium iron garnet and a microwave cavity mode. Strong coupling is achieved in the quantum regime where the average number of thermally or externally excited magnons and photons is less than one. We also confirm that the coupling strength is proportional to the square root of the number of spins. A nonmonotonic temperature dependence of the Kittel-mode linewidth is observed below 1 K and is attributed to the dissipation due to the coupling with a bath of two-level systems.
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Affiliation(s)
- Yutaka Tabuchi
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan
| | - Seiichiro Ishino
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan
| | - Toyofumi Ishikawa
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan
| | - Rekishu Yamazaki
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan
| | - Koji Usami
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan
| | - Yasunobu Nakamura
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan and Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198, Japan
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155
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Lin T, Tang C, Alyahayaei HM, Shi J. Experimental investigation of the nature of the magnetoresistance effects in Pd-YIG hybrid structures. PHYSICAL REVIEW LETTERS 2014; 113:037203. [PMID: 25083663 DOI: 10.1103/physrevlett.113.037203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Indexed: 06/03/2023]
Abstract
In bilayers consisting of Pd and yttrium iron garnet (Y(3)Fe(5)O(12) or YIG), we observe vanishingly small room-temperature conventional anisotropic magnetoresistance but large new magnetoresistance that is similar to the spin Hall magnetoresistance previously reported in Pt-YIG bilayers. We report a temperature dependence study of the two magnetoresistance effects in Pt-YIG bilayers. As the temperature is decreased, the new magnetoresistance shows a peak, whereas the anisotropic magnetoresistance effect starts to appear and increases monotonically. We find that the magnetoresistance peak shifts to lower temperatures in thicker Pd samples, a feature characteristic of the spin current effect. The distinct temperature dependence reveals fundamentally different mechanisms responsible for the two effects in such hybrid structures.
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Affiliation(s)
- Tao Lin
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Chi Tang
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Hamad M Alyahayaei
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Jing Shi
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
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156
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van Hoogdalem KA, Albert M, Simon P, Loss D. Proposal for a quantum magnetic RC circuit. PHYSICAL REVIEW LETTERS 2014; 113:037201. [PMID: 25083661 DOI: 10.1103/physrevlett.113.037201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Indexed: 06/03/2023]
Abstract
We propose a setup that is the spin analog of the charge-based quantum RC circuit. We define and compute the spin capacitance and the spin resistance of the circuit for both ferromagnetic and antiferromagnetic systems. We find that the antiferromagnetic setup has universal properties, but the ferromagnetic setup does not. We discuss how to use the proposed setup as a quantum source of spin excitations, and put forward two possible experimental realizations, using either ultracold atoms in optical lattices or artificially engineered atomic-spin chains.
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Affiliation(s)
- Kevin A van Hoogdalem
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Mathias Albert
- Laboratoire de Physique des Solides, CNRS, Université Paris-Sud, 91405 Orsay, France
| | - Pascal Simon
- Laboratoire de Physique des Solides, CNRS, Université Paris-Sud, 91405 Orsay, France
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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157
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Liao B, Zhou J, Chen G. Generalized two-temperature model for coupled phonon-magnon diffusion. PHYSICAL REVIEW LETTERS 2014; 113:025902. [PMID: 25062212 DOI: 10.1103/physrevlett.113.025902] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Indexed: 06/03/2023]
Abstract
We generalize the two-temperature model [Sanders and Walton, Phys. Rev. B 15, 1489 (1977)] for coupled phonon-magnon diffusion to include the effect of the concurrent magnetization flow, with a particular emphasis on the thermal consequence of the magnon flow driven by a nonuniform magnetic field. Working within the framework of the Boltzmann transport equation, we derive the constitutive equations for coupled phonon-magnon transport driven by gradients of both temperature and external magnetic fields, and the corresponding conservation laws. Our equations reduce to the original Sanders-Walton two-temperature model under a uniform external field, but predict a new magnon cooling effect driven by a nonuniform magnetic field in a homogeneous single-domain ferromagnet. We estimate the magnitude of the cooling effect in an yttrium iron garnet, and show it is within current experimental reach. With properly optimized materials, the predicted cooling effect can potentially supplement the conventional magnetocaloric effect in cryogenic applications in the future.
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Affiliation(s)
- Bolin Liao
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Jiawei Zhou
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Gang Chen
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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158
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Flipse J, Dejene FK, Wagenaar D, Bauer GEW, Ben Youssef J, van Wees BJ. Observation of the spin Peltier effect for magnetic insulators. PHYSICAL REVIEW LETTERS 2014; 113:027601. [PMID: 25062233 DOI: 10.1103/physrevlett.113.027601] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Indexed: 06/03/2023]
Abstract
We report the observation of the spin Peltier effect (SPE) in the ferrimagnetic insulator yttrium iron garnet (YIG), i.e., a heat current generated by a spin current flowing through a platinum (Pt)|YIG interface. The effect can be explained by the spin transfer torque that transforms the spin current in the Pt into a magnon current in the YIG. Via magnon-phonon interactions the magnetic fluctuations modulate the phonon temperature that is detected by a thermopile close to the interface. By finite-element modeling we verify the reciprocity between the spin Peltier and spin Seebeck effect. The observed strong coupling between thermal magnons and phonons in YIG is attractive for nanoscale cooling techniques.
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Affiliation(s)
- J Flipse
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - F K Dejene
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - D Wagenaar
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - G E W Bauer
- Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, The Netherlands and Institute for Materials Research and WPI-AIMR, Tohoku University, 980-8577 Sendai, Japan
| | - J Ben Youssef
- Université de Bretagne Occidentale, Laboratoire de Magnétisme de Bretagne CNRS, 6 Avenue Le Gorgeu, 29285 Brest, France
| | - B J van Wees
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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159
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Spin current generated by thermally driven ultrafast demagnetization. Nat Commun 2014; 5:4334. [PMID: 25007978 DOI: 10.1038/ncomms5334] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 06/06/2014] [Indexed: 11/08/2022] Open
Abstract
Spin current is the key element for nanoscale spintronic devices. For ultrafast operation of such nano-devices, generation of spin current in picoseconds, a timescale that is difficult to achieve using electrical circuits, is highly desired. Here we show thermally driven ultrafast demagnetization of a perpendicular ferromagnet leads to spin accumulation in a normal metal and spin transfer torque in an in-plane ferromagnet. The data are well described by models of spin generation and transport based on differences and gradients of thermodynamic parameters. The temperature difference between electrons and magnons is the driving force for spin current generation by ultrafast demagnetization. On longer timescales, a few picoseconds following laser excitation, we also observe a small contribution to spin current by a temperature gradient and the spin-dependent Seebeck effect.
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160
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Takei S, Tserkovnyak Y. Superfluid spin transport through easy-plane ferromagnetic insulators. PHYSICAL REVIEW LETTERS 2014; 112:227201. [PMID: 24949786 DOI: 10.1103/physrevlett.112.227201] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Indexed: 06/03/2023]
Abstract
Superfluid spin transport-dissipationless transport of spin-is theoretically studied in a ferromagnetic insulator with easy-plane anisotropy. We consider an open geometry where the spin current is injected into the ferromagnet from one side by a metallic reservoir with a nonequilibrium spin accumulation and ejected into another metallic reservoir located downstream. Spin transport is studied using a combination of magnetoelectric circuit theory, Landau-Lifshitz-Gilbert phenomenology, and microscopic linear-response theory. We discuss how spin superfluidity can be probed in a magnetically mediated negative electron-drag experiment.
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Affiliation(s)
- So Takei
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Yaroslav Tserkovnyak
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
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161
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Su Z, An Y, Wei X, Yang Z. Spin-dependent thermoelectronic transport of a single molecule magnet Mn(dmit)2. J Chem Phys 2014; 140:204707. [DOI: 10.1063/1.4879056] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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162
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Lin SZ, Batista CD, Reichhardt C, Saxena A. ac current generation in chiral magnetic insulators and Skyrmion motion induced by the spin Seebeck effect. PHYSICAL REVIEW LETTERS 2014; 112:187203. [PMID: 24856718 DOI: 10.1103/physrevlett.112.187203] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Indexed: 06/03/2023]
Abstract
We show that a temperature gradient induces an ac electric current in multiferroic insulators when the sample is embedded in a circuit. We also show that a thermal gradient can be used to move magnetic Skyrmions in insulating chiral magnets: the induced magnon flow from the hot to the cold region drives the Skyrmions in the opposite direction via a magnonic spin transfer torque. Both results are combined to compute the effect of Skyrmion motion on the ac current generation and demonstrate that Skyrmions in insulators are a promising route for spin caloritronics applications.
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Affiliation(s)
- Shi-Zeng Lin
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Cristian D Batista
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Charles Reichhardt
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Avadh Saxena
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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163
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Robust longitudinal spin-Seebeck effect in Bi-YIG thin films. Sci Rep 2014; 4:4429. [PMID: 24651124 PMCID: PMC3961741 DOI: 10.1038/srep04429] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 03/06/2014] [Indexed: 12/03/2022] Open
Abstract
In recent years, the coupling of magnetic insulators (bismuth-doped yttrium iron garnet, Bi-YIG) with platinum has garnered significant interest in spintronics research due to applicability as spin-current-driven thermoelectric coatings. These coatings bridge the gap between spintronics technologies and thermoelectric materials, providing a novel means of transforming waste heat into electricity. However, there remain questions regarding the origins of the spin-Seebeck effect (SSE) as well as claims that observed effects are a manifestation of magnetic proximity effects, which would induce magnetic behavior in platinum. Herewith we provide support that the voltages observed in the Bi-YIG/Pt films are purely SSE voltages. We reaffirm claims that magnon transport theory provides an ample basis for explaining SSE behavior. Finally, we illustrate the advantages of pulsed-laser deposition, as these Bi-YIG films possess large SSE voltages (even in absence of an external magnetic field), as much as twice those of films fabricated via solution-based methods.
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164
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Ultrahigh spin thermopower and pure spin current in a single-molecule magnet. Sci Rep 2014; 4:4128. [PMID: 24549224 PMCID: PMC3928577 DOI: 10.1038/srep04128] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 01/30/2014] [Indexed: 11/30/2022] Open
Abstract
Using the non-equilibrium Green's function (NEGF) formalism within the sequential regime, we studied ultrahigh spin thermopower and pure spin current in single-molecule magnet(SMM), which is attached to nonmagnetic metal wires with spin bias and angle (θ) between the easy axis of SMM and the spin orientation in the electrodes. A pure spin current can be generated by tuning the gate voltage and temperature difference with finite spin bias and the arbitrary angle except of . In the linear regime, large thermopower can be obtained by modifying Vg and the angles (θ). These results are useful in fabricating and advantaging SMM devices based on spin caloritronics.
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165
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Borlenghi S, Wang W, Fangohr H, Bergqvist L, Delin A. Designing a spin-Seebeck diode. PHYSICAL REVIEW LETTERS 2014; 112:047203. [PMID: 24580487 DOI: 10.1103/physrevlett.112.047203] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Indexed: 06/03/2023]
Abstract
Using micromagnetic simulations, we have investigated spin dynamics in a spin-valve bilayer in the presence of a thermal gradient. The direction and the intensity of the gradient allow us to excite the spin wave modes of each layer selectively. This permits us to synchronize the magnetization precession of the two layers and to rectify the flows of energy and magnetization through the system. Our study yields promising opportunities for applications in spin caloritronics and nanophononics devices.
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Affiliation(s)
- Simone Borlenghi
- Department of Materials and Nanophysics, School of Information and Communication Technology, Electrum 229, Royal Institute of Technology, SE-16440 Kista, Sweden
| | - Weiwei Wang
- Engineering and the Environment, University of Southampton, SO17 1BJ Southampton, United Kingdom
| | - Hans Fangohr
- Engineering and the Environment, University of Southampton, SO17 1BJ Southampton, United Kingdom
| | - Lars Bergqvist
- Department of Materials and Nanophysics, School of Information and Communication Technology, Electrum 229, Royal Institute of Technology, SE-16440 Kista, Sweden and SeRC (Swedish e-Science Research Center), KTH, SE-10044 Stockholm, Sweden
| | - Anna Delin
- Department of Materials and Nanophysics, School of Information and Communication Technology, Electrum 229, Royal Institute of Technology, SE-16440 Kista, Sweden and SeRC (Swedish e-Science Research Center), KTH, SE-10044 Stockholm, Sweden and Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
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166
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Wang X, Tian W, Liao M, Bando Y, Golberg D. Recent advances in solution-processed inorganic nanofilm photodetectors. Chem Soc Rev 2014; 43:1400-22. [DOI: 10.1039/c3cs60348b] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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167
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Ni Y, Yao K, Fu H, Gao G, Zhu S, Wang S. Spin seebeck effect and thermal colossal magnetoresistance in graphene nanoribbon heterojunction. Sci Rep 2013; 3:1380. [PMID: 23459307 PMCID: PMC3587885 DOI: 10.1038/srep01380] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 02/20/2013] [Indexed: 11/25/2022] Open
Abstract
Spin caloritronics devices are very important for future development of low-power-consumption technology. We propose a new spin caloritronics device based on zigzag graphene nanoribbon (ZGNR), which is a heterojunction consisting of single-hydrogen-terminated ZGNR (ZGNR-H) and double-hydrogen-terminated ZGNR (ZGNR-H2). We predict that spin-up and spin-down currents flowing in opposite directions can be induced by temperature difference instead of external electrical bias. The thermal spin-up current is considerably large and greatly improved compared with previous work in graphene. Moreover, the thermal colossal magnetoresistance is obtained in our research, which could be used to fabricate highly-efficient spin caloritronics MR devices.
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Affiliation(s)
- Yun Ni
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China
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168
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Schmid M, Srichandan S, Meier D, Kuschel T, Schmalhorst JM, Vogel M, Reiss G, Strunk C, Back CH. Transverse spin Seebeck effect versus anomalous and planar Nernst effects in Permalloy thin films. PHYSICAL REVIEW LETTERS 2013; 111:187201. [PMID: 24237554 DOI: 10.1103/physrevlett.111.187201] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 06/18/2013] [Indexed: 06/02/2023]
Abstract
Transverse magnetothermoelectric effects are studied in Permalloy thin films grown on MgO and GaAs substrates and compared to those grown on suspended SiN(x) membranes. The transverse voltage along platinum strips patterned on top of the Permalloy films is measured versus the external magnetic field as a function of the angle and temperature gradients. After the identification of the contribution of the planar and anomalous Nernst effects, we find an upper limit for the transverse spin Seebeck effect, which is several orders of magnitude smaller than previously reported.
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Affiliation(s)
- M Schmid
- Institute of Experimental and Applied Physics, University of Regensburg, D-93040 Regensburg, Germany
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169
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Weiler M, Althammer M, Schreier M, Lotze J, Pernpeintner M, Meyer S, Huebl H, Gross R, Kamra A, Xiao J, Chen YT, Jiao H, Bauer GEW, Goennenwein STB. Experimental test of the spin mixing interface conductivity concept. PHYSICAL REVIEW LETTERS 2013; 111:176601. [PMID: 24206509 DOI: 10.1103/physrevlett.111.176601] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Indexed: 05/20/2023]
Abstract
We perform a quantitative, comparative study of the spin pumping, spin Seebeck, and spin Hall magnetoresistance effects, all detected via the inverse spin Hall effect in a series of over 20 yttrium iron garnet/Pt samples. Our experimental results fully support present, exclusively spin current-based, theoretical models using a single set of plausible parameters for spin mixing conductance, spin Hall angle, and spin diffusion length. Our findings establish the purely spintronic nature of the aforementioned effects and provide a quantitative description, in particular, of the spin Seebeck effect.
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Affiliation(s)
- Mathias Weiler
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
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170
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Tserkovnyak Y. Spintronics: an insulator-based transistor. NATURE NANOTECHNOLOGY 2013; 8:706-707. [PMID: 24091453 DOI: 10.1038/nnano.2013.203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Affiliation(s)
- Yaroslav Tserkovnyak
- Department of Physics and Astronomy, University of California Los Angeles, California 90095-1547, USA
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171
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Heyderman LJ, Stamps RL. Artificial ferroic systems: novel functionality from structure, interactions and dynamics. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:363201. [PMID: 23948652 DOI: 10.1088/0953-8984/25/36/363201] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Lithographic processing and film growth technologies are continuing to advance, so that it is now possible to create patterned ferroic materials consisting of arrays of sub-1 μm elements with high definition. Some of the most fascinating behaviour of these arrays can be realised by exploiting interactions between the individual elements to create new functionality. The properties of these artificial ferroic systems differ strikingly from those of their constituent components, with novel emergent behaviour arising from the collective dynamics of the interacting elements, which are arranged in specific designs and can be activated by applying magnetic or electric fields. We first focus on artificial spin systems consisting of arrays of dipolar-coupled nanomagnets and, in particular, review the field of artificial spin ice, which demonstrates a wide range of fascinating phenomena arising from the frustration inherent in particular arrangements of nanomagnets, including emergent magnetic monopoles, domains of ordered macrospins, and novel avalanche behaviour. We outline how demagnetisation protocols have been employed as an effective thermal anneal in an attempt to reach the ground state, comment on phenomena that arise in thermally activated systems and discuss strategies for selectively generating specific configurations using applied magnetic fields. We then move on from slow field and temperature driven dynamics to high frequency phenomena, discussing spinwave excitations in the context of magnonic crystals constructed from arrays of patterned magnetic elements. At high frequencies, these arrays are studied in terms of potential applications including magnetic logic, linear and non-linear microwave optics, and fast, efficient switching, and we consider the possibility to create tunable magnonic crystals with artificial spin ice. Finally, we discuss how functional ferroic composites can be incorporated to realise magnetoelectric effects. Specifically, we discuss artificial multiferroics (or multiferroic composites), which hold promise for new applications that involve electric field control of magnetism, or electric and magnetic field responsive devices for high frequency integrated circuit design in microwave and terahertz signal processing. We close with comments on how enhanced functionality can be realised through engineering of nanostructures with interacting ferroic components, creating opportunities for novel spin electronic devices that, for example, make use of the transport of magnetic charges, thermally activated elements, and reprogrammable nanomagnet systems.
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Affiliation(s)
- L J Heyderman
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
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172
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Sun Y, Chang H, Kabatek M, Song YY, Wang Z, Jantz M, Schneider W, Wu M, Montoya E, Kardasz B, Heinrich B, te Velthuis SGE, Schultheiss H, Hoffmann A. Damping in yttrium iron garnet nanoscale films capped by platinum. PHYSICAL REVIEW LETTERS 2013; 111:106601. [PMID: 25166689 DOI: 10.1103/physrevlett.111.106601] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 03/29/2013] [Indexed: 06/03/2023]
Abstract
Strong damping enhancement in nm-thick yttrium iron garnet (YIG) films due to Pt capping layers was observed. This damping is substantially larger than the expected damping due to conventional spin pumping, is accompanied by a shift in the ferromagnetic resonance field, and can be suppressed by the use of a Cu spacer in between the YIG and Pt films. The data indicate that such damping may originate from the ferromagnetic ordering in Pt atomic layers near the YIG/Pt interface and the dynamic exchange coupling between the ordered Pt spins and the spins in the YIG film.
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Affiliation(s)
- Yiyan Sun
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Houchen Chang
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Michael Kabatek
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Young-Yeal Song
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Zihui Wang
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Michael Jantz
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - William Schneider
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Mingzhong Wu
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - E Montoya
- Physics Department, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - B Kardasz
- Physics Department, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - B Heinrich
- Physics Department, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | | | - Helmut Schultheiss
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Axel Hoffmann
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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173
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Agrawal M, Vasyuchka VI, Serga AA, Karenowska AD, Melkov GA, Hillebrands B. Direct measurement of magnon temperature: new insight into magnon-phonon coupling in magnetic insulators. PHYSICAL REVIEW LETTERS 2013; 111:107204. [PMID: 25166706 DOI: 10.1103/physrevlett.111.107204] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Indexed: 06/03/2023]
Abstract
We present spatially resolved measurements of the magnon temperature in a magnetic insulator subject to a thermal gradient. Our data reveal an unexpectedly close correspondence between the spatial dependencies of the exchange magnon and phonon temperatures. These results indicate that if--as is currently thought--the transverse spin Seebeck effect is caused by a temperature difference between the magnon and phonon baths, it must be the case that the magnon temperature is spectrally nonuniform and that the effect is driven by the sparsely populated dipolar region of the magnon spectrum.
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Affiliation(s)
- M Agrawal
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany and Graduate School Materials Science in Mainz, Gottlieb-Daimer-Strasse 47, 67663 Kaiserslautern, Germany
| | - V I Vasyuchka
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
| | - A A Serga
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
| | - A D Karenowska
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - G A Melkov
- Faculty of Radiophysics, Taras Shevchenko National University of Kyiv, 01601 Kyiv, Ukraine
| | - B Hillebrands
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
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174
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Brechet SD, Vetro FA, Papa E, Barnes SE, Ansermet JP. Evidence for a magnetic Seebeck effect. PHYSICAL REVIEW LETTERS 2013; 111:087205. [PMID: 24010472 DOI: 10.1103/physrevlett.111.087205] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Indexed: 06/02/2023]
Abstract
The irreversible thermodynamics of a continuous medium with magnetic dipoles predicts that a temperature gradient in the presence of magnetization waves induces a magnetic induction field, which is the magnetic analog of the Seebeck effect. This thermal gradient modulates the precession and relaxation. The magnetic Seebeck effect implies that magnetization waves propagating in the direction of the temperature gradient and the external magnetic induction field are less attenuated, while magnetization waves propagating in the opposite direction are more attenuated.
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Affiliation(s)
- Sylvain D Brechet
- Institute of Condensed Matter Physics, Station 3, Ecole Polytechnique Fédérale de Lausanne-EPFL, CH-1015 Lausanne, Switzerland
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175
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Miao BF, Huang SY, Qu D, Chien CL. Inverse spin Hall effect in a ferromagnetic metal. PHYSICAL REVIEW LETTERS 2013; 111:066602. [PMID: 23971597 DOI: 10.1103/physrevlett.111.066602] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Indexed: 06/02/2023]
Abstract
The inverse spin Hall effect (ISHE) has been observed only in nonmagnetic metals, such as Pt and Au, with a strong spin-orbit coupling. We report the observation of ISHE in a ferromagnetic permalloy (Py) on ferromagnetic insulator yttrium iron garnet (YIG). Through controlling the spin current injection by altering the Py-YIG interface, we have isolated the spin current contribution and demonstrated the ISHE in a ferromagnetic metal, the reciprocal phenomenon of the anomalous Hall effect. A large spin Hall angle in Py, determined from Py thin films of different thicknesses, indicates many other ferromagnetic metals may be exploited as superior pure spin current detectors and for applications in spin current.
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Affiliation(s)
- B F Miao
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
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176
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Tikhonov KS, Sinova J, Finkel’stein AM. Spectral non-uniform temperature and non-local heat transfer in the spin Seebeck effect. Nat Commun 2013; 4:1945. [PMID: 23735931 DOI: 10.1038/ncomms2945] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 04/30/2013] [Indexed: 11/09/2022] Open
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177
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An T, Vasyuchka VI, Uchida K, Chumak AV, Yamaguchi K, Harii K, Ohe J, Jungfleisch MB, Kajiwara Y, Adachi H, Hillebrands B, Maekawa S, Saitoh E. Unidirectional spin-wave heat conveyer. NATURE MATERIALS 2013; 12:549-553. [PMID: 23603850 DOI: 10.1038/nmat3628] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 03/12/2013] [Indexed: 06/02/2023]
Abstract
When energy is introduced into a region of matter, it heats up and the local temperature increases. This energy spontaneously diffuses away from the heated region. In general, heat should flow from warmer to cooler regions and it is not possible to externally change the direction of heat conduction. Here we show a magnetically controllable heat flow caused by a spin-wave current. The direction of the flow can be switched by applying a magnetic field. When microwave energy is applied to a region of ferrimagnetic Y3Fe5O12, an end of the magnet far from this region is found to be heated in a controlled manner and a negative temperature gradient towards it is formed. This is due to unidirectional energy transfer by the excitation of spin-wave modes without time-reversal symmetry and to the conversion of spin waves into heat. When a Y3Fe5O12 film with low damping coefficients is used, spin waves are observed to emit heat at the sample end up to 10 mm away from the excitation source. The magnetically controlled remote heating we observe is directly applicable to the fabrication of a heat-flow controller.
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Affiliation(s)
- T An
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
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178
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Boehnke A, Walter M, Roschewsky N, Eggebrecht T, Drewello V, Rott K, Münzenberg M, Thomas A, Reiss G. Time-resolved measurement of the tunnel magneto-Seebeck effect in a single magnetic tunnel junction. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:063905. [PMID: 23822355 DOI: 10.1063/1.4811130] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Recently, several groups have reported spin-dependent thermoelectric effects in magnetic tunnel junctions. In this paper, we present a setup for time-resolved measurements of thermovoltages and thermocurrents of a single micro- to nanometer-scaled tunnel junction. An electrically modulated diode laser is used to create a temperature gradient across the tunnel junction layer stack. This laser modulation technique enables the recording of time-dependent thermovoltage signals with a temporal resolution only limited by the preamplifier for the thermovoltage. So far, time-dependent thermovoltage could not be interpreted. Now, with the setup presented in this paper, it is possible to distinguish different Seebeck voltage contributions to the overall measured voltage signal in the μs time regime. A model circuit is developed that explains those voltage contributions on different sample types. Further, it will be shown that a voltage signal arising from the magnetic tunnel junction can only be observed when the laser spot is directly centered on top of the magnetic tunnel junction, which allows a lateral separation of the effects.
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Affiliation(s)
- Alexander Boehnke
- Thin Films and Physics of Nanostructures, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany.
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179
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Nakayama H, Althammer M, Chen YT, Uchida K, Kajiwara Y, Kikuchi D, Ohtani T, Geprägs S, Opel M, Takahashi S, Gross R, Bauer GEW, Goennenwein STB, Saitoh E. Spin Hall magnetoresistance induced by a nonequilibrium proximity effect. PHYSICAL REVIEW LETTERS 2013; 110:206601. [PMID: 25167435 DOI: 10.1103/physrevb.87.144411] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Indexed: 05/27/2023]
Abstract
We report anisotropic magnetoresistance in Pt|Y(3)Fe(5)O(12) bilayers. In spite of Y(3)Fe(5)O(12) being a very good electrical insulator, the resistance of the Pt layer reflects its magnetization direction. The effect persists even when a Cu layer is inserted between Pt and Y(3)Fe(5)O(12), excluding the contribution of induced equilibrium magnetization at the interface. Instead, we show that the effect originates from concerted actions of the direct and inverse spin Hall effects and therefore call it "spin Hall magnetoresistance."
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Affiliation(s)
- H Nakayama
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan
| | - M Althammer
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany and Center for Materials Information Technology MINT and Department of Chemistry, University of Alabama, Tuscaloosa, Alabama 35487, USA
| | - Y-T Chen
- Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, The Netherlands
| | - K Uchida
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - Y Kajiwara
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - D Kikuchi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - T Ohtani
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - S Geprägs
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
| | - M Opel
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
| | - S Takahashi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - R Gross
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany and Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - G E W Bauer
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, The Netherlands and WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - S T B Goennenwein
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
| | - E Saitoh
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and CREST, Japan Science and Technology Agency, Tokyo 102-0076, Japan and The Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
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180
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Nakayama H, Althammer M, Chen YT, Uchida K, Kajiwara Y, Kikuchi D, Ohtani T, Geprägs S, Opel M, Takahashi S, Gross R, Bauer GEW, Goennenwein STB, Saitoh E. Spin Hall magnetoresistance induced by a nonequilibrium proximity effect. PHYSICAL REVIEW LETTERS 2013; 110:206601. [PMID: 25167435 DOI: 10.1103/physrevlett.110.206601] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Indexed: 06/03/2023]
Abstract
We report anisotropic magnetoresistance in Pt|Y(3)Fe(5)O(12) bilayers. In spite of Y(3)Fe(5)O(12) being a very good electrical insulator, the resistance of the Pt layer reflects its magnetization direction. The effect persists even when a Cu layer is inserted between Pt and Y(3)Fe(5)O(12), excluding the contribution of induced equilibrium magnetization at the interface. Instead, we show that the effect originates from concerted actions of the direct and inverse spin Hall effects and therefore call it "spin Hall magnetoresistance."
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Affiliation(s)
- H Nakayama
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan
| | - M Althammer
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany and Center for Materials Information Technology MINT and Department of Chemistry, University of Alabama, Tuscaloosa, Alabama 35487, USA
| | - Y-T Chen
- Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, The Netherlands
| | - K Uchida
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - Y Kajiwara
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - D Kikuchi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - T Ohtani
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - S Geprägs
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
| | - M Opel
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
| | - S Takahashi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - R Gross
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany and Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - G E W Bauer
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, The Netherlands and WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - S T B Goennenwein
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
| | - E Saitoh
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan and CREST, Japan Science and Technology Agency, Tokyo 102-0076, Japan and The Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
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181
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Jiang W, Upadhyaya P, Fan Y, Zhao J, Wang M, Chang LT, Lang M, Wong KL, Lewis M, Lin YT, Tang J, Cherepov S, Zhou X, Tserkovnyak Y, Schwartz RN, Wang KL. Direct imaging of thermally driven domain wall motion in magnetic insulators. PHYSICAL REVIEW LETTERS 2013; 110:177202. [PMID: 23679764 DOI: 10.1103/physrevlett.110.177202] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Indexed: 06/02/2023]
Abstract
Thermally induced domain wall motion in a magnetic insulator was observed using spatiotemporally resolved polar magneto-optical Kerr effect microscopy. The following results were found: (i) the domain wall moves towards hot regime; (ii) a threshold temperature gradient (5 K/mm), i.e., a minimal temperature gradient required to induce domain wall motion; (iii) a finite domain wall velocity outside of the region with a temperature gradient, slowly decreasing as a function of distance, which is interpreted to result from the penetration of a magnonic current into the constant temperature region; and (iv) a linear dependence of the average domain wall velocity on temperature gradient, beyond a threshold thermal bias. Our observations can be qualitatively explained using a magnonic spin transfer torque mechanism, which suggests the utility of magnonic spin transfer torque for controlling magnetization dynamics.
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Affiliation(s)
- Wanjun Jiang
- Department of Electrical Engineering, Device Research Laboratory, University of California, Los Angeles, California 90095, USA
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182
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Adachi H, Uchida KI, Saitoh E, Maekawa S. Theory of the spin Seebeck effect. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2013; 76:036501. [PMID: 23420561 DOI: 10.1088/0034-4885/76/3/036501] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The spin Seebeck effect refers to the generation of a spin voltage caused by a temperature gradient in a ferromagnet, which enables the thermal injection of spin currents from the ferromagnet into an attached nonmagnetic metal over a macroscopic scale of several millimeters. The inverse spin Hall effect converts the injected spin current into a transverse charge voltage, thereby producing electromotive force as in the conventional charge Seebeck device. Recent theoretical and experimental efforts have shown that the magnon and phonon degrees of freedom play crucial roles in the spin Seebeck effect. In this paper, we present the theoretical basis for understanding the spin Seebeck effect and briefly discuss other thermal spin effects.
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Affiliation(s)
- Hiroto Adachi
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Ibaraki, Japan.
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183
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Qu D, Huang SY, Hu J, Wu R, Chien CL. Intrinsic spin Seebeck effect in Au/YIG. PHYSICAL REVIEW LETTERS 2013; 110:067206. [PMID: 23432301 DOI: 10.1103/physrevlett.110.067206] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Indexed: 06/01/2023]
Abstract
The acute magnetic proximity effects in Pt/YIG compromise the suitability of Pt as a spin current detector. We show that Au/YIG, with no anomalous Hall effect and a negligible magnetoresistance, allows the measurements of the intrinsic spin Seebeck effect with a magnitude much smaller than that in Pt/YIG. The experiment results are consistent with the spin polarized density functional calculations for Pt with a sizable and Au with a negligible magnetic moment near the interface with YIG.
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Affiliation(s)
- D Qu
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
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184
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Kikkawa T, Uchida K, Shiomi Y, Qiu Z, Hou D, Tian D, Nakayama H, Jin XF, Saitoh E. Longitudinal spin Seebeck effect free from the proximity Nernst effect. PHYSICAL REVIEW LETTERS 2013; 110:067207. [PMID: 23432302 DOI: 10.1103/physrevlett.110.067207] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Indexed: 06/01/2023]
Abstract
This Letter provides evidence for intrinsic longitudinal spin Seebeck effects (LSSEs) that are free from the anomalous Nernst effect (ANE) caused by an extrinsic proximity effect. We report the observation of LSSEs in Au/Y(3)Fe(5)O(12) (YIG) and Pt/Cu/YIG systems, showing that the LSSE appears even when the mechanism of the proximity ANE is clearly removed. In the conventional Pt/YIG structure, furthermore, we separate the LSSE from the ANE by comparing the voltages in different magnetization and temperature-gradient configurations; the ANE contamination was found to be negligibly small even in the Pt/YIG structure.
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Affiliation(s)
- T Kikkawa
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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185
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Zeng M, Huang W, Liang G. Spin-dependent thermoelectric effects in graphene-based spin valves. NANOSCALE 2013; 5:200-208. [PMID: 23151965 DOI: 10.1039/c2nr32226a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Using first-principles calculations combined with non-equilibrium Green's function (NEGF), we investigate spin-dependent thermoelectric effects in a spin valve which consists of zigzag graphene nanoribbon (ZGNR) electrodes with different magnetic configurations. We find that electron transport properties in the ZGNR-based spin valve are strongly dependent on the magnetic configurations. As a result, with a temperature bias, thermally-induced currents can be controlled by switching the magnetic configurations, indicating a thermal magnetoresistance (MR) effect. Moreover, based on the linear response assumption, our study shows that the remarkably different Seebeck coefficients in the various magnetic configurations lead to a very large and controllable magneto Seebeck ratio. In addition, we evaluate thermoelectric properties, such as the power factor, electron thermal conductance and figure of merit (ZT), of the ZGNR-based spin valve. Our results indicate that the power factor and the electron thermal conductance are strongly related to the transmission gap and electron-hole symmetry of the transmission spectrum. Moreover, the value of ZT can reach 0.15 at room temperature without considering phonon scattering. In addition, we investigate the thermally-controlled magnetic distributions in the ZGNR-based spin valve and find that the magnetic distribution, especially the local magnetic moment around the Ni atom, is strongly related to the thermal bias. The very large, multi-valued and controllable thermal magnetoresistance and Seebeck effects indicate the strong potential of ZGNR-based spin valves for extremely low-power consuming spin caloritronics applications. The thermally-controlled magnetic moment in the ZGNR-based spin valve indicates its possible applications for information storage.
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Affiliation(s)
- Minggang Zeng
- Department of Electrical and Computer Engineering, 4 Engineering Drive 3, National University of Singapore, Singapore 117576, Republic of Singapore.
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186
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Avery AD, Pufall MR, Zink BL. Observation of the planar Nernst effect in permalloy and nickel thin films with in-plane thermal gradients. PHYSICAL REVIEW LETTERS 2012; 109:196602. [PMID: 23215412 DOI: 10.1103/physrevlett.109.196602] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Indexed: 06/01/2023]
Abstract
We present experimental evidence of a transverse thermopower, or planar Nernst effect, in ferromagnetic metal thin films driven by thermal gradients applied in the plane of the films. Samples of 20 nm thick Ni and Ni(80)Fe(20) were deposited on 500 nm thick suspended Si-N thermal isolation platforms with integrated platinum strips designed originally to allow measurement of thermally generated spin currents (the spin Seebeck effect). The low thermal conductivity of the thin supporting Si-N structure results in an essentially 2D geometry that approaches the zero substrate limit, dramatically reducing the contribution of thermal gradients perpendicular to the sample plane typically found in similar experiments on bulk substrates. The voltage on the platinum strips generated transverse to the applied thermal gradient (V(T)) is linear with increasing ΔT and exhibits a sign reversal on hot and cold sides of the sample. However, V(T) is always even in applied magnetic field and shows a sinθ cosθ angular dependence, both key indicators of the planar Nernst effect. Within the 5 nV estimated error of our experiment there is no evidence of a signal from the spin Seebeck effect, which would have cosθ angular dependence, suggesting a reduced spin Seebeck coefficient in a planar, entirely thin-film geometry.
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Affiliation(s)
- A D Avery
- Department of Physics and Astronomy, University of Denver, Denver, Colorado 80208, USA
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187
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Wei D, Niimi Y, Gu B, Ziman T, Maekawa S, Otani Y. The spin Hall effect as a probe of nonlinear spin fluctuations. Nat Commun 2012; 3:1058. [DOI: 10.1038/ncomms2063] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 08/14/2012] [Indexed: 11/09/2022] Open
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188
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Huang SY, Fan X, Qu D, Chen YP, Wang WG, Wu J, Chen TY, Xiao JQ, Chien CL. Transport magnetic proximity effects in platinum. PHYSICAL REVIEW LETTERS 2012; 109:107204. [PMID: 23005323 DOI: 10.1103/physrevlett.109.107204] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Indexed: 06/01/2023]
Abstract
Platinum (Pt) metal, being nonmagnetic and with a strong spin-orbit coupling interaction, has been central in detecting the pure spin current and establishing most of the recent spin-based phenomena. Magnetotransport measurements, both electrical and thermal, conclusively show strong ferromagnetic characteristics in thin Pt films on the ferromagnetic insulator due to the magnetic proximity effects. The pure spin current phenomena measured by Pt, including the inverse spin Hall and the spin Seebeck effects, are thus contaminated and not exclusively established.
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Affiliation(s)
- S Y Huang
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
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189
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Zhang SSL, Zhang S. Magnon mediated electric current drag across a ferromagnetic insulator layer. PHYSICAL REVIEW LETTERS 2012; 109:096603. [PMID: 23002868 DOI: 10.1103/physrevlett.109.096603] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Indexed: 06/01/2023]
Abstract
In a semiconductor heterostructure, the Coulomb interaction is responsible for the electric current drag between two 2D electron gases across an electron impenetrable insulator. For two metallic layers separated by a ferromagnetic insulator (FI) layer, the electric current drag can be mediated by a nonequilibrium magnon current of the FI. We determine the drag current by using the semiclassical Boltzmann approach with proper boundary conditions of electrons and magnons at the metal-FI interface.
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Affiliation(s)
- Steven S-L Zhang
- Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
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190
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Tauber K, Gradhand M, Fedorov DV, Mertig I. Extrinsic spin Nernst effect from first principles. PHYSICAL REVIEW LETTERS 2012; 109:026601. [PMID: 23030189 DOI: 10.1103/physrevlett.109.026601] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Indexed: 06/01/2023]
Abstract
We present an ab initio description of the thermal transport phenomenon called the spin Nernst effect. It refers to generation of a spin accumulation or a pure spin current transverse to an applied temperature gradient. This is similar to the intensively studied spin Hall effect described by intrinsic and extrinsic mechanisms due to an applied electric field. Analogously, several contributions are present for the spin Nernst effect. Here we investigate the extrinsic skew scattering mechanism which is dominant in the limit of dilute alloys. Our calculations are based on a fully relativistic Korringa-Kohn-Rostoker method and a solution of the linearized Boltzmann equation. As a first application, we consider a Cu host with Au, Ti, and Bi impurities.
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Affiliation(s)
- Katarina Tauber
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
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191
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Jaworski CM, Myers RC, Johnston-Halperin E, Heremans JP. Giant spin Seebeck effect in a non-magnetic material. Nature 2012; 487:210-3. [PMID: 22785317 DOI: 10.1038/nature11221] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 05/08/2012] [Indexed: 11/09/2022]
Abstract
The spin Seebeck effect is observed when a thermal gradient applied to a spin-polarized material leads to a spatially varying transverse spin current in an adjacent non-spin-polarized material, where it gets converted into a measurable voltage. It has been previously observed with a magnitude of microvolts per kelvin in magnetically ordered materials, ferromagnetic metals, semiconductors and insulators. Here we describe a signal in a non-magnetic semiconductor (InSb) that has the hallmarks of being produced by the spin Seebeck effect, but is three orders of magnitude larger (millivolts per kelvin). We refer to the phenomenon that produces it as the giant spin Seebeck effect. Quantizing magnetic fields spin-polarize conduction electrons in semiconductors by means of Zeeman splitting, which spin-orbit coupling amplifies by a factor of ∼25 in InSb. We propose that the giant spin Seebeck effect is mediated by phonon-electron drag, which changes the electrons' momentum and directly modifies the spin-splitting energy through spin-orbit interactions. Owing to the simultaneously strong phonon-electron drag and spin-orbit coupling in InSb, the magnitude of the giant spin Seebeck voltage is comparable to the largest known classical thermopower values.
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Affiliation(s)
- C M Jaworski
- Department of Mechanical Engineering, The Ohio State University, Columbus, Ohio 43210, USA
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192
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193
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Lu L, Sun Y, Jantz M, Wu M. Control of ferromagnetic relaxation in magnetic thin films through thermally induced interfacial spin transfer. PHYSICAL REVIEW LETTERS 2012; 108:257202. [PMID: 23004648 DOI: 10.1103/physrevlett.108.257202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Indexed: 06/01/2023]
Abstract
Relaxation control in magnetic thin films via thermally induced interfacial spin transfers was demonstrated for the first time. The experiments used a trilayered structure that consisted of an yttrium iron garnet (YIG) thin film grown on a gadolinium gallium garnet substrate and capped with a nanometer-thick Pt layer. As a temperature gradient is applied across the thickness of the structure, there exists a spin angular momentum transfer across the YIG/Pt interface. This spin transfer results in a torque on YIG magnetic moments. The torque can either speed up or slow down the relaxation in the YIG film, depending on the sign of the temperature gradient with respect to the trilayered structure.
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Affiliation(s)
- Lei Lu
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
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194
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Kirihara A, Uchida KI, Kajiwara Y, Ishida M, Nakamura Y, Manako T, Saitoh E, Yorozu S. Spin-current-driven thermoelectric coating. NATURE MATERIALS 2012; 11:686-689. [PMID: 22706614 DOI: 10.1038/nmat3360] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 05/17/2012] [Indexed: 06/01/2023]
Abstract
Energy harvesting technologies, which generate electricity from environmental energy, have been attracting great interest because of their potential to power ubiquitously deployed sensor networks and mobile electronics. Of these technologies, thermoelectric (TE) conversion is a particularly promising candidate, because it can directly generate electricity from the thermal energy that is available in various places. Here we show a novel TE concept based on the spin Seebeck effect, called 'spin-thermoelectric (STE) coating', which is characterized by a simple film structure, convenient scaling capability, and easy fabrication. The STE coating, with a 60-nm-thick bismuth-substituted yttrium iron garnet (Bi:YIG) film, is applied by means of a highly efficient process on a non-magnetic substrate. Notably, spin-current-driven TE conversion is successfully demonstrated under a temperature gradient perpendicular to such an ultrathin STE-coating layer (amounting to only 0.01% of the total sample thickness). We also show that the STE coating is applicable even on glass surfaces with amorphous structures. Such a versatile implementation of the TE function may pave the way for novel applications making full use of omnipresent heat.
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Affiliation(s)
- Akihiro Kirihara
- Smart Energy Research Laboratories, NEC Corporation, Tsukuba 305-8501, Japan
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195
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Bender SA, Duine RA, Tserkovnyak Y. Electronic pumping of quasiequilibrium Bose-Einstein-condensed magnons. PHYSICAL REVIEW LETTERS 2012; 108:246601. [PMID: 23004301 DOI: 10.1103/physrevlett.108.246601] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Indexed: 06/01/2023]
Abstract
We theoretically investigate spin transfer between a system of quasiequilibrated Bose-Einstein-condensed magnons in an insulator in direct contact with a conductor. While charge transfer is prohibited across the interface, spin transport arises from the exchange coupling between insulator and conductor spins. In a normal insulator phase, spin transport is governed solely by the presence of thermal and spin-diffusive gradients; the presence of Bose-Einstein condensation (BEC), meanwhile, gives rise to a temperature-independent condensate spin current. Depending on the thermodynamic bias of the system, spin may flow in either direction across the interface, engendering the possibility of a dynamical phase transition of magnons. We discuss the experimental feasibility of observing a BEC steady state (fomented by a spin Seebeck effect), which is contrasted to the more familiar spin-transfer-induced classical instabilities.
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Affiliation(s)
- Scott A Bender
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
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196
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Weiler M, Huebl H, Goerg FS, Czeschka FD, Gross R, Goennenwein STB. Spin pumping with coherent elastic waves. PHYSICAL REVIEW LETTERS 2012; 108:176601. [PMID: 22680888 DOI: 10.1103/physrevlett.108.176601] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Indexed: 06/01/2023]
Abstract
We show that the resonant coupling of phonons and magnons can be exploited to generate spin currents at room temperature. Surface acoustic wave pulses with a frequency of 1.55 GHz and duration of 300 ns provide coherent elastic waves in a ferromagnetic thin-film-normal-metal (Co/Pt) bilayer. We use the inverse spin Hall voltage in the Pt as a measure for the spin current and record its evolution as a function of time and external magnetic field magnitude and orientation. Our experiments show that a spin current is generated in the exclusive presence of a resonant elastic excitation. This establishes acoustic spin pumping as a resonant analogue to the spin Seebeck effect.
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Affiliation(s)
- M Weiler
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
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197
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Jungwirth T, Wunderlich J, Olejník K. Spin Hall effect devices. NATURE MATERIALS 2012; 11:382-90. [PMID: 22522638 DOI: 10.1038/nmat3279] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The spin Hall effect is a relativistic spin-orbit coupling phenomenon that can be used to electrically generate or detect spin currents in non-magnetic systems. Here we review the experimental results that, since the first experimental observation of the spin Hall effect less than 10 years ago, have established the basic physical understanding of the phenomenon, and the role that several of the spin Hall devices have had in the demonstration of spintronic functionalities and physical phenomena. We have attempted to organize the experiments in a chronological order, while simultaneously dividing the Review into sections on semiconductor or metal spin Hall devices, and on optical or electrical spin Hall experiments. The spin Hall device studies are placed in a broader context of the field of spin injection, manipulation, and detection in non-magnetic conductors.
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Affiliation(s)
- Tomas Jungwirth
- Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic
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198
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Abstract
Spintronics is about the coupled electron spin and charge transport in condensed-matter structures and devices. The recently invigorated field of spin caloritronics focuses on the interaction of spins with heat currents, motivated by newly discovered physical effects and strategies to improve existing thermoelectric devices. Here we give an overview of our understanding and the experimental state-of-the-art concerning the coupling of spin, charge and heat currents in magnetic thin films and nanostructures. Known phenomena are classified either as independent electron (such as spin-dependent Seebeck) effects in metals that can be understood by a model of two parallel spin-transport channels with different thermoelectric properties, or as collective (such as spin Seebeck) effects, caused by spin waves, that also exist in insulating ferromagnets. The search to find applications--for example heat sensors and waste heat recyclers--is on.
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Affiliation(s)
- Gerrit E W Bauer
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
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199
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Bakker FL, Flipse J, Slachter A, Wagenaar D, van Wees BJ. Thermoelectric detection of ferromagnetic resonance of a nanoscale ferromagnet. PHYSICAL REVIEW LETTERS 2012; 108:167602. [PMID: 22680756 DOI: 10.1103/physrevlett.108.167602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Indexed: 06/01/2023]
Abstract
We present thermoelectric measurements of the heat dissipated due to ferromagnetic resonance of a Permalloy strip. A microwave magnetic field, produced by an on-chip coplanar strip waveguide, is used to drive the magnetization precession. The generated heat is detected via Seebeck measurements on a thermocouple connected to the ferromagnet. The observed resonance peak shape is in agreement with the Landau-Lifshitz-Gilbert equation and is compared with thermoelectric finite-element modeling. Unlike other methods, this technique is not restricted to electrically conductive media and is therefore also applicable to for instance ferromagnetic insulators.
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Affiliation(s)
- F L Bakker
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, The Netherlands.
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200
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Lin W, Hehn M, Chaput L, Negulescu B, Andrieu S, Montaigne F, Mangin S. Giant spin-dependent thermoelectric effect in magnetic tunnel junctions. Nat Commun 2012; 3:744. [DOI: 10.1038/ncomms1748] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 02/13/2012] [Indexed: 11/09/2022] Open
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