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Useinov N. Tunnel magnetoresistance and spin transfer torque in magnetic tunnel junction with embedded nanoparticles. EPJ WEB OF CONFERENCES 2018. [DOI: 10.1051/epjconf/201818501015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The theoretical model of spin-dependent transport in magnetic tunnel junctions (MTJ) containing magnetic or non-magnetic nanoparticle is developed. The dependences of tunnel magnetoresistance (TMR) and in-plane component of spin transfer torque (STT) on the applied voltage for various sizes of nanoparticles of the order of the mean free path of the conduction electron are calculated. The calculation is performed in the approximation of the ballistic transport of conduction electrons through the insulating layers of the MTJ and the nanoparticles.
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Useinov A, Lin HH, Lai CH. Symmetric and Asymmetric Magnetic Tunnel Junctions with Embedded Nanoparticles: Effects of Size Distribution and Temperature on Tunneling Magnetoresistance and Spin Transfer Torque. Sci Rep 2017; 7:8357. [PMID: 28827591 PMCID: PMC5566438 DOI: 10.1038/s41598-017-08354-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 07/06/2017] [Indexed: 11/09/2022] Open
Abstract
The problem of the ballistic electron tunneling is considered in magnetic tunnel junction with embedded non-magnetic nanoparticles (NP-MTJ), which creates additional conducting middle layer. The strong temperature impact was found in the system with averaged NP diameter d av < 1.8 nm. Temperature simulation is consistent with experimental observations showing the transition between dip and classical dome-like tunneling magnetoresistance (TMR) voltage behaviors. The low temperature approach also predicts step-like TMR and quantized in-plane spin transfer torque (STT) effects. The robust asymmetric STT respond is found due to voltage sign inversion in NP-MTJs with barrier asymmetry. Furthermore, it is shown how size distribution of NPs as well as quantization rules modify the spin-current filtering properties of the nanoparticles in ballistic regime. Different quantization rules for the transverse component of the wave vector are considered to overpass the dimensional threshold (d av ≈ 1.8 nm) between quantum well and bulk-assisted states of the middle layer.
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Affiliation(s)
- Arthur Useinov
- Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.,Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan.,Institute of Physics, Kazan Federal University, Kazan, Russian Federation
| | - Hsiu-Hau Lin
- Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
| | - Chih-Huang Lai
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan.
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Temple RC, McLaren M, Brydson RMD, Hickey BJ, Marrows CH. Long spin lifetime and large barrier polarisation in single electron transport through a CoFe nanoparticle. Sci Rep 2016; 6:28296. [PMID: 27329575 PMCID: PMC4916452 DOI: 10.1038/srep28296] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 05/25/2016] [Indexed: 11/09/2022] Open
Abstract
We have investigated single electron spin transport in individual single crystal bcc Co30Fe70 nanoparticles using scanning tunnelling microscopy with a standard tungsten tip. Particles were deposited using a gas-aggregation nanoparticle source and individually addressed as asymmetric double tunnel junctions with both a vacuum and a MgO tunnel barrier. Spectroscopy measurements on the particles show a Coulomb staircase that is correlated with the measured particle size. Field emission tunnelling effects are incorporated into standard single electron theory to model the data. This formalism allows spin-dependent parameters to be determined even though the tip is not spin-polarised. The barrier spin polarisation is very high, in excess of 84%. By variation of the resistance, several orders of magnitude of the system timescale are probed, enabling us to determine the spin relaxation time on the island. It is found to be close to 10 μs, a value much longer than previously reported.
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Affiliation(s)
- R C Temple
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
| | - M McLaren
- Institute for Materials Research, School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - R M D Brydson
- Institute for Materials Research, School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - B J Hickey
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
| | - C H Marrows
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
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Zheng C, Shull RD, Chen PJ, Pong PWT. Kondo Effect in Magnetic Tunnel Junctions with an AlO x Tunnel Barrier. PHYSICS LETTERS. A 2016; 380:2237-2241. [PMID: 28690361 PMCID: PMC5497476 DOI: 10.1016/j.physleta.2016.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The influence of the magnetization configuration on Kondo effect in magnetic tunnel junction is investigated. In the parallel configuration, an additional resistance contribution (R*) below 40 K exhibits a logarithmic temperature dependence, indicating the presence of Kondo effect. However, in the anti-parallel configuration, the Kondo-effect-associated spin-flip scattering has a nontrivial contribution to the tunneling current, which compensates the reduction of the current directly caused by Kondo scattering, making R* disappear. These results indicate that suppression and restoration of Kondo effect can be experimentally achieved by altering the magnetization configuration, enhancing our understanding of the role of Kondo effect in spin-dependent transport.
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Affiliation(s)
- Chao Zheng
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong
| | - Robert D. Shull
- Functional Nanostructured Materials Group, National Institute of Standards and Technology, Gaithersburg, MD 20899–8552, United States
| | - P. J. Chen
- Functional Nanostructured Materials Group, National Institute of Standards and Technology, Gaithersburg, MD 20899–8552, United States
| | - Philip W. T. Pong
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong
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Useinov A, Ye LX, Useinov N, Wu TH, Lai CH. Anomalous Tunnel Magnetoresistance and Spin Transfer Torque in Magnetic Tunnel Junctions with Embedded Nanoparticles. Sci Rep 2015; 5:18026. [PMID: 26681336 PMCID: PMC4683539 DOI: 10.1038/srep18026] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 11/09/2015] [Indexed: 11/09/2022] Open
Abstract
The tunnel magnetoresistance (TMR) in the magnetic tunnel junction (MTJ) with embedded nanoparticles (NPs) was calculated in range of the quantum-ballistic model. The simulation was performed for electron tunneling through the insulating layer with embedded magnetic and non-magnetic NPs within the approach of the double barrier subsystem connected in parallel to the single barrier one. This model can be applied for both MTJs with in-plane magnetization and perpendicular one. We also calculated the in-plane component of the spin transfer torque (STT) versus the applied voltage in MTJs with magnetic NPs and determined that its value can be much larger than in single barrier system (SBS) for the same tunneling thickness. The reported simulation reproduces experimental data of the TMR suppression and peak-like TMR anomalies at low voltages available in leterature.
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Affiliation(s)
- Arthur Useinov
- Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.,Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan.,Institute of Physics, Kazan Federal University, Kazan, Russian Federation
| | - Lin-Xiu Ye
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan
| | - Niazbeck Useinov
- Institute of Physics, Kazan Federal University, Kazan, Russian Federation
| | - Te-Ho Wu
- Graduate School of Materials Science, National Yunlin University of Science and Technology, Douliou, Taiwan
| | - Chih-Huang Lai
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan
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O'Brien L, Erickson MJ, Spivak D, Ambaye H, Goyette RJ, Lauter V, Crowell PA, Leighton C. Kondo physics in non-local metallic spin transport devices. Nat Commun 2014; 5:3927. [PMID: 24873934 DOI: 10.1038/ncomms4927] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 04/22/2014] [Indexed: 11/09/2022] Open
Abstract
The non-local spin-valve is pivotal in spintronics, enabling separation of charge and spin currents, disruptive potential applications and the study of pressing problems in the physics of spin injection and relaxation. Primary among these problems is the perplexing non-monotonicity in the temperature-dependent spin accumulation in non-local ferromagnetic/non-magnetic metal structures, where the spin signal decreases at low temperatures. Here we show that this effect is strongly correlated with the ability of the ferromagnetic to form dilute local magnetic moments in the NM. This we achieve by studying a significantly expanded range of ferromagnetic/non-magnetic combinations. We argue that local moments, formed by ferromagnetic/non-magnetic interdiffusion, suppress the injected spin polarization and diffusion length via a manifestation of the Kondo effect, thus explaining all observations. We further show that this suppression can be completely quenched, even at interfaces that are highly susceptible to the effect, by insertion of a thin non-moment-supporting interlayer.
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Affiliation(s)
- L O'Brien
- 1] Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA [2] Thin Film Magnetism, Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - M J Erickson
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - D Spivak
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - H Ambaye
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - R J Goyette
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - V Lauter
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - P A Crowell
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Halley D, Najjari N, Majjad H, Joly L, Ohresser P, Scheurer F, Ulhaq-Bouillet C, Berciaud S, Doudin B, Henry Y. Size-induced enhanced magnetoelectric effect and multiferroicity in chromium oxide nanoclusters. Nat Commun 2014; 5:3167. [PMID: 24452260 DOI: 10.1038/ncomms4167] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 12/20/2013] [Indexed: 11/09/2022] Open
Abstract
The control of the magnetization of a material with an electric field would make the design and the integration of novel electronic devices possible. This explains the renewed interest in multiferroic materials. Progress in this field is currently hampered by the scarcity of the materials available and the smallness of the magnetoelectric effects. Here we present a proof-of-principle experiment showing that engineering large strains through nanoscale size reduction is an efficient route for increasing magnetoelectric coefficients by orders of magnitude. The archetype magnetoelectric material, Cr2O3, in the form of epitaxial clusters, exhibits an unprecedented 600% change in magnetization magnitude under 1 V. Furthermore, a multiferroic phase, with both magnetic and electric spontaneous polarizations, is found in the clusters, while absent in the bulk.
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Affiliation(s)
- D Halley
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2, France
| | - N Najjari
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2, France
| | - H Majjad
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2, France
| | - L Joly
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2, France
| | - P Ohresser
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette, France
| | - F Scheurer
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2, France
| | - C Ulhaq-Bouillet
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2, France
| | - S Berciaud
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2, France
| | - B Doudin
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2, France
| | - Y Henry
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2, France
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Pauly M, Dayen JF, Golubev D, Beaufrand JB, Pichon BP, Doudin B, Bégin-Colin S. Co-tunneling enhancement of the electrical response of nanoparticle networks. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2012; 8:108-15. [PMID: 22095862 DOI: 10.1002/smll.201100931] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 08/08/2011] [Indexed: 05/10/2023]
Abstract
A co-tunneling charge-transfer process dominates the electrical properties of a nanometer-sized "slice" in a nanoparticle network, which results in universal scaling of the conductance with temperature and bias voltage, as well as enhanced spintronics properties. By designing two large (10 μm) electrodes with short (60 nm) separation, access is obtained to transport dominated by charge transfer involving "nanoslices" made of three nanoparticles only. Magnetic iron oxide nanoparticle networks exhibit a magnetoresistance ratio that is not reachable by tunneling or hopping processes, thereby illustrating how such a size-matched planar device with dominant co-tunneling charge-transfer process is optimal for realizing multifunctional devices with enhanced change of conductance under external stimulus.
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Affiliation(s)
- Matthias Pauly
- Institut de Physique et Chimie des Matériaux de Strasbourg, CNRS-UdS-UMR 7504, 23 rue du Loess, BP 43, 67034 Strasbourg cedex 2, France
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Dempsey KJ, Ciudad D, Marrows CH. Single electron spintronics. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2011; 369:3150-3174. [PMID: 21727119 DOI: 10.1098/rsta.2011.0105] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Single electron electronics is now well developed, and allows the manipulation of electrons one-by-one as they tunnel on and off a nanoscale conducting island. In the past decade or so, there have been concerted efforts in several laboratories to construct single electron devices incorporating ferromagnetic components in order to introduce spin functionality. The use of ferromagnetic electrodes with a non-magnetic island can lead to spin accumulation on the island. On the other hand, making the dot also ferromagnetic introduces new physics such as tunnelling magnetoresistance enhancement in the cotunnelling regime and manifestations of the Kondo effect. Such nanoscale islands are also found to have long spin lifetimes. Conventional spintronics makes use of the average spin-polarization of a large ensemble of electrons: this new approach offers the prospect of accessing the quantum properties of the electron, and is a candidate approach to the construction of solid-state spin-based qubits.
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Affiliation(s)
- Kari J Dempsey
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
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Yang H, Yang SH, Qi DC, Rusydi A, Kawai H, Saeys M, Leo T, Smith DJ, Parkin SSP. Negative tunneling magnetoresistance by canted magnetization in MgO/NiO tunnel barriers. PHYSICAL REVIEW LETTERS 2011; 106:167201. [PMID: 21599406 DOI: 10.1103/physrevlett.106.167201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Indexed: 05/30/2023]
Abstract
The influence of the insertion of an ultrathin NiO layer between the MgO barrier and the ferromagnetic electrodes in magnetic tunnel junctions has been investigated from measurements of the tunneling magnetoresistance and via x-ray magnetic circular dichroism (XMCD). The magnetoresistance shows a high asymmetry with respect to bias voltage, giving rise to a negative value of up to -16% at 2.8 K. We attribute this effect to the formation of noncollinear spin structures at the interface of the NiO layer as inferred from XMCD measurements. The magnetic moments of the interface Ni atoms tilt from their easy axis due to exchange coupling with the neighboring ferromagnetic electrode, and the tilting angle decreases with increasing NiO thickness. The experimental observations are further supported by noncollinear spin density functional calculations.
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Affiliation(s)
- Hyunsoo Yang
- Department of Electrical and Computer Engineering and NUSNNI-NanoCore, National University of Singapore, Singapore, Singapore.
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Weymann I. The tunnel magnetoresistance in chains of quantum dots weakly coupled to external leads. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:015301. [PMID: 21386221 DOI: 10.1088/0953-8984/22/1/015301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We analyze numerically the spin-dependent transport through coherent chains of three coupled quantum dots weakly connected to external magnetic leads. In particular, using the diagrammatic technique on the Keldysh contour, we calculate the conductance, shot noise and tunnel magnetoresistance (TMR) in the sequential and cotunneling regimes. We show that transport characteristics greatly depend on the strength of the interdot Coulomb correlations, which determines the spatial distribution of the electron wavefunction in the chain. When the correlations are relatively strong, depending on the transport regime, we find both negative TMR as well as TMR enhanced above the Julliere value, accompanied with negative differential conductance (NDC) and super-Poissonian shot noise. This nontrivial behavior of tunnel magnetoresistance is associated with selection rules that govern tunneling processes and various high-spin states of the chain that are relevant for transport. For weak interdot correlations, on the other hand, the TMR is always positive and not larger than the Julliere TMR, although super-Poissonian shot noise and NDC can still be observed.
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Affiliation(s)
- Ireneusz Weymann
- Physics Department, Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität, Munich, Germany.
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Gao L, Jiang X, Yang SH, Rice PM, Topuria T, Parkin SSP. Increased tunneling magnetoresistance using normally bcc CoFe alloy electrodes made amorphous without glass forming additives. PHYSICAL REVIEW LETTERS 2009; 102:247205. [PMID: 19659044 DOI: 10.1103/physrevlett.102.247205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Indexed: 05/28/2023]
Abstract
Using cross-section transmission electron microscopy we show that films of CoFe alloys, sandwiched between two conventional amorphous materials, are amorphous when less than approximately 25-30 A thick. When these amorphous layers are integrated into magnetic tunnel junctions with amorphous alumina tunnel barriers, significantly higher tunneling magnetoresistance is found compared to when these layers are made crystalline (e.g., by heating or by thickening them). We postulate that this is likely due to changes in interfacial bonding at the alumina-CoFe interface. Indeed, x-ray emission spectroscopy shows a significant increase in the Fe, but not the Co, 3d density of states at the Fermi energy for thin amorphous CoFe layers.
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Affiliation(s)
- Li Gao
- IBM Research Division, Almaden Research Center, San Jose, California 95120, USA
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