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Thermally active nanoparticle clusters enslaved by engineered domain wall traps. Nat Commun 2021; 12:5813. [PMID: 34608137 PMCID: PMC8490384 DOI: 10.1038/s41467-021-25931-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 09/09/2021] [Indexed: 11/08/2022] Open
Abstract
The stable assembly of fluctuating nanoparticle clusters on a surface represents a technological challenge of widespread interest for both fundamental and applied research. Here we demonstrate a technique to stably confine in two dimensions clusters of interacting nanoparticles via size-tunable, virtual magnetic traps. We use cylindrical Bloch walls arranged to form a triangular lattice of ferromagnetic domains within an epitaxially grown ferrite garnet film. At each domain, the magnetic stray field generates an effective harmonic potential with a field tunable stiffness. The experiments are combined with theory to show that the magnetic confinement is effectively harmonic and pairwise interactions are of dipolar nature, leading to central, strictly repulsive forces. For clusters of magnetic nanoparticles, the stationary collective states arise from the competition between repulsion, confinement and the tendency to fill the central potential well. Using a numerical simulation model as a quantitative map between the experiments and theory we explore the field-induced crystallization process for larger clusters and unveil the existence of three different dynamical regimes. The present method provides a model platform for investigations of the collective phenomena emerging when strongly confined nanoparticle clusters are forced to move in an idealized, harmonic-like potential.
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Siddiqui SA, Dutta S, Tang A, Liu L, Ross CA, Baldo MA. Magnetic Domain Wall Based Synaptic and Activation Function Generator for Neuromorphic Accelerators. NANO LETTERS 2020; 20:1033-1040. [PMID: 31888336 DOI: 10.1021/acs.nanolett.9b04200] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Magnetic domain walls are information tokens in both logic and memory devices and hold particular interest in applications such as neuromorphic accelerators that combine logic in memory. Here, we show that devices based on the electrical manipulation of magnetic domain walls are capable of implementing linear, as well as programmable nonlinear, functions. Unlike other approaches, domain-wall-based devices are ideal for application to both synaptic weight generators and thresholding in deep neural networks. Prototype micrometer-size devices operate with 8 ns current pulses and the energy consumption required for weight modulation is ≤16 pJ. Both speed and energy consumption compare favorably to other synaptic nonvolatile devices, with the expected energy dissipation for scaled 20 nm devices close to that of biological neurons.
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Affiliation(s)
- Saima A Siddiqui
- Department of Electrical Engineering and Computer Science , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Sumit Dutta
- Department of Electrical Engineering and Computer Science , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Astera Tang
- Department of Materials Science and Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Luqiao Liu
- Department of Electrical Engineering and Computer Science , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Caroline A Ross
- Department of Materials Science and Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Marc A Baldo
- Department of Electrical Engineering and Computer Science , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
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Grünewald A, Kumar KR, Sue CM. New insights into the complex role of mitochondria in Parkinson’s disease. Prog Neurobiol 2019; 177:73-93. [DOI: 10.1016/j.pneurobio.2018.09.003] [Citation(s) in RCA: 176] [Impact Index Per Article: 35.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Revised: 07/09/2018] [Accepted: 09/10/2018] [Indexed: 02/07/2023]
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Stoop RL, Straube AV, Tierno P. Enhancing Nanoparticle Diffusion on a Unidirectional Domain Wall Magnetic Ratchet. NANO LETTERS 2019; 19:433-440. [PMID: 30484652 DOI: 10.1021/acs.nanolett.8b04248] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The performance of nanoscale magnetic devices is often limited by the presence of thermal fluctuations, whereas in micro- and nanofluidic applications the same fluctuations may be used to spread reactants or drugs. Here, we demonstrate the controlled motion and the enhancement of diffusion of magnetic nanoparticles that are manipulated and driven across a series of Bloch walls within an epitaxially grown ferrite garnet film. We use a rotating magnetic field to generate a traveling wave potential that unidirectionally transports the nanoparticles at a frequency tunable speed. Strikingly, we find an enhancement of diffusion along the propulsion direction and a frequency-dependent diffusion coefficient that can be precisely controlled by varying the system parameters. To explain the reported phenomena, we develop a theoretical approach that shows a fair agreement with the experimental data enabling an exact analytical expression for the enhanced diffusivity above the magnetically modulated periodic landscape. Our technique to control thermal fluctuations of driven magnetic nanoparticles represents a versatile and powerful way to programmably transport magnetic colloidal matter in a fluid, opening the doors to different fluidic applications based on exploiting magnetic domain wall ratchets.
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Affiliation(s)
- Ralph L Stoop
- Departament de Física de la Matèria Condensada , Universitat de Barcelona , Avenida Diagonal 647 , 08028 Barcelona , Spain
| | - Arthur V Straube
- Departament de Física de la Matèria Condensada , Universitat de Barcelona , Avenida Diagonal 647 , 08028 Barcelona , Spain
- Department of Mathematics and Computer Science , Freie Universität Berlin , Arnimalle 6 , 14195 Berlin , Germany
| | - Pietro Tierno
- Departament de Física de la Matèria Condensada , Universitat de Barcelona , Avenida Diagonal 647 , 08028 Barcelona , Spain
- Institut de Nanociència i Nanotecnologia , Universitat de Barcelona , 08028 Barcelona , Spain
- Universitat de Barcelona Institute of Complex Systems (UBICS) , Universitat de Barcelona , 08028 Barcelona , Spain
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Dutta S, Siddiqui SA, Currivan-Incorvia JA, Ross CA, Baldo MA. The Spatial Resolution Limit for an Individual Domain Wall in Magnetic Nanowires. NANO LETTERS 2017; 17:5869-5874. [PMID: 28813156 DOI: 10.1021/acs.nanolett.7b03199] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Magnetic nanowires are the foundation of several promising nonvolatile computing devices, most notably magnetic racetrack memory and domain wall logic. Here, we determine the analog information capacity in these technologies, analyzing a magnetic nanowire containing a single domain wall. Although wires can be deliberately patterned with notches to define discrete positions for domain walls, the line edge roughness of the wire can also trap domain walls at dimensions below the resolution of the fabrication process, determining the fundamental resolution limit for the placement of a domain wall. Using a fractal model for the edge roughness, we show theoretically and experimentally that the analog information capacity for wires is limited by the self-affine statistics of the wire edge roughness, a relevant result for domain wall devices scaled to regimes where edge roughness dominates the energy landscape in which the walls move.
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Pfeiffer A, Reeve RM, Voto M, Savero-Torres W, Richter N, Vila L, Attané JP, Lopez-Diaz L, Kläui M. Geometrical control of pure spin current induced domain wall depinning. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:085802. [PMID: 28001132 DOI: 10.1088/1361-648x/aa5516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We investigate the pure spin-current assisted depinning of magnetic domain walls in half ring based Py/Al lateral spin valve structures. Our optimized geometry incorporating a patterned notch in the detector electrode, directly below the Al spin conduit, provides a tailored pinning potential for a transverse domain wall and allows for a precise control over the magnetization configuration and as a result the domain wall pinning. Due to the patterned notch, we are able to study the depinning field as a function of the applied external field for certain applied current densities and observe a clear asymmetry for the two opposite field directions. Micromagnetic simulations show that this can be explained by the asymmetry of the pinning potential. By direct comparison of the calculated efficiencies for different external field and spin current directions, we are able to disentangle the different contributions from the spin transfer torque, Joule heating and the Oersted field. The observed high efficiency of the pure spin current induced spin transfer torque allows for a complete depinning of the domain wall at zero external field for a charge current density of [Formula: see text] A m-2, which is attributed to the optimal control of the position of the domain wall.
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Affiliation(s)
- A Pfeiffer
- Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany. Graduate School of Excellence Materials Science in Mainz (MAINZ), Staudinger Weg 9, 55128 Mainz, Germany
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Tierno P, Johansen TH, Sancho JM. A Tunable Magnetic Domain Wall Conduit Regulating Nanoparticle Diffusion. NANO LETTERS 2016; 16:5169-5175. [PMID: 27434042 DOI: 10.1021/acs.nanolett.6b02112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate a general and robust method to confine on a plane strongly diffusing nanoparticles in water by using size tunable magnetic channels. These virtual conduits are realized with pairs of movable Bloch walls located within an epitaxially grown ferrite garnet film. We show that once inside the magnetic conduit the particles experience an effective local parabolic potential in the transverse direction, while freely diffusing along the conduit. The stiffness of the magnetic potential is determined as a function of field amplitude that varies the width of the magnetic channel. Precise control of the degree of confinement is demonstrated by tuning the applied field. The magnetic conduit is then used to realize single files of nonpassing particles and to induce periodic condensation of an ensemble of particles into parallel stripes in a completely controllable and reversible manner.
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Affiliation(s)
- Pietro Tierno
- Departament de Física de la Matèria Condensada, Universitat de Barcelona , Avenida Diagonal 647, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona , Barcelona, Spain
- Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona , Barcelona, Spain
| | - Tom H Johansen
- Department of Physics, The University of Oslo , P.O. Box 1048 Blindern, 0316 Oslo, Norway
- Institute for Superconducting and Electronic Materials, University of Wollongong , Wollongong, New South Wales 2522, Australia
| | - José M Sancho
- Departament de Física de la Matèria Condensada, Universitat de Barcelona , Avenida Diagonal 647, 08028 Barcelona, Spain
- Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona , Barcelona, Spain
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Kim S, Lee S, Hong J. An array of ferromagnetic nanoislands nondestructively patterned via a local phase transformation by low-energy proton irradiation. ACS NANO 2014; 8:4698-4704. [PMID: 24754781 DOI: 10.1021/nn500683b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Low-energy proton irradiation was applied to pattern an array of metallic, ferromagnetic nanoislands through the local phase transformation of an oxidic, paramagnetic phase in a complex superlattice composed of repetitions of an oxidic and metallic layer. The irradiation inflicted minimal damage on the structure, resulting in the absence of unwanted defects and side effects. This nondestructive pattern transfer was clearly confirmed by the contrast between irradiated and unirradiated regions in electrical, chemical, and magnetic images. Simulation based on the magnetic properties suggests that this low-energy proton irradiation can nondestructively pattern an array of ferromagnetic islands with 8.2 nm in diameter and 7.4 nm in spacing between islands, which means it can achieve an areal density of ∼3 Tb/in.(2) with a thermal stability of over 80 kBT. Such an array is strong enough to overcome the so-called superparamagnetism limit in magnetic recording. The attributes demonstrated here corroborate that proton irradiation can be applied to design and pattern devices on a nanometer scale not only for magnetic but also for electric and optical materials systems in all such systems in which a local phase transformation is available.
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Affiliation(s)
- Sanghoon Kim
- Materials Science and Engineering, Yonsei University , Seoul 120-749, Korea
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Bisig A, Stärk M, Mawass MA, Moutafis C, Rhensius J, Heidler J, Büttner F, Noske M, Weigand M, Eisebitt S, Tyliszczak T, Van Waeyenberge B, Stoll H, Schütz G, Kläui M. Correlation between spin structure oscillations and domain wall velocities. Nat Commun 2013; 4:2328. [PMID: 23978905 PMCID: PMC3759078 DOI: 10.1038/ncomms3328] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 07/19/2013] [Indexed: 11/09/2022] Open
Abstract
Magnetic sensing and logic devices based on the motion of magnetic domain walls rely on the precise and deterministic control of the position and the velocity of individual magnetic domain walls in curved nanowires. Varying domain wall velocities have been predicted to result from intrinsic effects such as oscillating domain wall spin structure transformations and extrinsic pinning due to imperfections. Here we use direct dynamic imaging of the nanoscale spin structure that allows us for the first time to directly check these predictions. We find a new regime of oscillating domain wall motion even below the Walker breakdown correlated with periodic spin structure changes. We show that the extrinsic pinning from imperfections in the nanowire only affects slow domain walls and we identify the magnetostatic energy, which scales with the domain wall velocity, as the energy reservoir for the domain wall to overcome the local pinning potential landscape.
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Affiliation(s)
- André Bisig
- 1] Department of Physics, University of Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany [2] Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany [3] SwissFEL, Paul Scherrer Institute, 5232 Villigen, Switzerland and Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland [4] Institut für Physik, Johannes Gutenberg Universität Mainz, 55128 Mainz, Germany
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Abstract
In ferromagnetic nanostructures domain walls as emergent entities separate uniformly magnetized regions. They are describable as quasi particles and can be controlled by magnetic fields or spin-polarized currents. Below critical driving forces domain walls are rigid conserving their spin structure. Like other quasi particles internal excitations influence the domain wall dynamics above a critical velocity known as the Walker breakdown. This complex nonlinear motion has not been observed directly. Here we present direct time-resolved x-ray microscopy of structural transformations of domain walls during motion. Although governed by nonlinear dynamics the displacement of the wall on the observed time scale can still be described by an analytical model. Using a reduced dynamical domain-wall width the model enables us to determine the mass of a vortex wall experimentally. Further we observe the creation and the mutual annihilation of domain walls. The intrinsic nanometer length and nanosecond time-scales are determined directly.
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Suppression of the intrinsic stochastic pinning of domain walls in magnetic nanostripes. Nat Commun 2011; 2:562. [PMID: 22127058 PMCID: PMC3482628 DOI: 10.1038/ncomms1575] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 10/28/2011] [Indexed: 11/21/2022] Open
Abstract
Nanofabrication has allowed the development of new concepts such as magnetic logic and race-track memory, both of which are based on the displacement of magnetic domain walls on magnetic nanostripes. One of the issues that has to be solved before devices can meet the market demands is the stochastic behaviour of the domain wall movement in magnetic nanostripes. Here we show that the stochastic nature of the domain wall motion in permalloy nanostripes can be suppressed at very low fields (0.6–2.7 Oe). We also find different field regimes for this stochastic motion that match well with the domain wall propagation modes. The highest pinning probability is found around the precessional mode and, interestingly, it does not depend on the external field in this regime. These results constitute an experimental evidence of the intrinsic nature of the stochastic pinning of domain walls in soft magnetic nanostripes. The propagation of magnetic domain walls in nanowires offers promise as the basis of future memory storage technologies. Muñoz and Prieto show that the random pinning of domain walls to structural defects in the nanowires can be suppressed at low fields, thus improving the reliability of the transmission of the domain walls substantially.
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