ORCID Profile
0000-0001-7283-6884
Current Organisation
UNSW Sydney
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Condensed Matter Physics | Electronic and Magnetic Properties of Condensed Matter; Superconductivity | Condensed Matter Modelling and Density Functional Theory
Publisher: American Physical Society (APS)
Date: 21-03-2013
Publisher: American Chemical Society (ACS)
Date: 04-05-2023
Publisher: Springer Science and Business Media LLC
Date: 25-10-2018
DOI: 10.1038/S41598-018-33780-6
Abstract: We experimentally study the structure and dynamics of magnetic domains in synthetic antiferromagnets based on Co/Ru/Co films. Dramatic effects arise from the interaction among the topological defects comprising the dual domain walls in these structures. Under applied magnetic fields, the dual domain walls propagate following the dynamics of bi-meronic (bi-vortex/bi-antivortex) topological defects built in the walls. Application of an external field triggers a rich dynamical response: The propagation depends on mutual orientation and chirality of bi-vortices and bi-antivortices in the domain walls. For certain configurations, we observe sudden jumps of composite domain walls in increasing field, which are associated with the decay of composite skyrmions. These features allow for the enhanced control of domain-wall motion in synthetic antiferromagnets with the potential of employing them as information carriers in future logic and storage devices.
Publisher: American Physical Society (APS)
Date: 26-04-2019
Publisher: Elsevier BV
Date: 02-2021
Publisher: American Physical Society (APS)
Date: 11-06-2012
Publisher: American Physical Society (APS)
Date: 09-08-2023
Publisher: American Physical Society (APS)
Date: 14-02-2003
Publisher: American Physical Society (APS)
Date: 22-01-2010
Publisher: American Physical Society (APS)
Date: 30-08-2018
Publisher: AIP Publishing
Date: 28-03-2016
DOI: 10.1063/1.4944996
Abstract: Domain wall dynamics in a magnetoelectric antiferromagnet is analyzed, and its implications for magnetoelectric memory applications are discussed. Cr2O3 is used in the estimates of the materials parameters. It is found that the domain wall mobility has a maximum as a function of the electric field due to the gyrotropic coupling induced by it. In Cr2O3, the maximal mobility of 0.1 m/(s Oe) is reached at E≈0.06 V/nm. Fields of this order may be too weak to overcome the intrinsic depinning field, which is estimated for B-doped Cr2O3. These major drawbacks for device implementation can be overcome by applying a small in-plane shear strain, which blocks the domain wall precession. Domain wall mobility of about 0.7 m/(s Oe) can then be achieved at E = 0.2 V/nm. A split-gate scheme is proposed for the domain-wall controlled bit element its extension to multiple-gate linear arrays can offer advantages in memory density, programmability, and logic functionality.
Publisher: American Physical Society (APS)
Date: 04-10-2010
Publisher: American Physical Society (APS)
Date: 16-10-2017
Publisher: Springer Science and Business Media LLC
Date: 09-11-2020
DOI: 10.1038/S41524-020-00435-Y
Abstract: A magnetic bimeron is an in-plane topological counterpart of a magnetic skyrmion. Despite the topological equivalence, their statics and dynamics could be distinct, making them attractive from the perspectives of both physics and spintronic applications. In this work, we demonstrate the stabilization of bimeron solitons and clusters in the antiferromagnetic (AFM) thin film with interfacial Dzyaloshinskii–Moriya interaction (DMI). Bimerons demonstrate high current-driven mobility as generic AFM solitons, while featuring anisotropic and relativistic dynamics excited by currents with in-plane and out-of-plane polarizations, respectively. Moreover, these spin textures can absorb other bimeron solitons or clusters along the translational direction to acquire a wide range of Néel topological numbers. The clustering involves the rearrangement of topological structures, and gives rise to remarkable changes in static and dynamical properties. The merits of AFM bimeron clusters reveal a potential path to unify multibit data creation, transmission, storage, and even topology-based computation within the same material system, and may stimulate spintronic devices enabling innovative paradigms of data manipulations.
Publisher: AIP Publishing
Date: 28-01-2019
DOI: 10.1063/1.5080302
Abstract: Skyrmion-based spin torque nano-oscillators are potential next-generation microwave signal generators. However, ferromagnetic skyrmion-based spin torque nano-oscillators cannot reach high oscillation frequencies. In this work, we propose to use the circular motion of an antiferromagnetic skyrmion to create an oscillation signal in order to overcome this obstacle. Micromagnetic simulations demonstrate that the antiferromagnetic skyrmion-based spin torque nano-oscillators can produce high frequencies (tens of GHz). Furthermore, the speed of the circular motion for an antiferromagnetic skyrmion in a nanodisk is analytically derived, which agrees well with the results of numerical simulations. Our findings are useful for the understanding of the inertial dynamics of an antiferromagnetic skyrmion and the development of future skyrmion-based spin torque nano-oscillators.
Publisher: American Physical Society (APS)
Date: 15-12-2021
Publisher: American Physical Society (APS)
Date: 22-02-2016
Publisher: American Physical Society (APS)
Date: 30-06-2023
Publisher: Elsevier BV
Date: 06-2015
Publisher: Elsevier BV
Date: 07-2019
Publisher: AIP Publishing
Date: 06-07-2020
DOI: 10.1063/5.0012706
Abstract: Magnetic skyrmionium can be used as a nanometer-scale non-volatile information carrier, which shows no skyrmion Hall effect due to its special structure carrying zero topological charge. Here, we report the static and dynamic properties of an isolated nanoscale skyrmionium in a frustrated magnetic monolayer, where the skyrmionium is stabilized by competing interactions. The frustrated skyrmionium has a size of about 10 nm, which can be further reduced by tuning perpendicular magnetic anisotropy or the magnetic field. It is found that the nanoscale skyrmionium driven by the d ing-like spin-orbit torque shows directional motion with a favored Bloch-type helicity. A small driving current or magnetic field can lead to the transformation of an unstable Néel-type skyrmionium to a metastable Bloch-type skyrmionium. A large driving current may result in the distortion and collapse of the Bloch-type skyrmionium. Our results are useful for the understanding of frustrated skyrmionium physics, which also provide guidelines for the design of spintronic devices based on topological spin textures.
Publisher: American Physical Society (APS)
Date: 31-07-2014
Publisher: American Physical Society (APS)
Date: 14-11-2022
Publisher: American Physical Society (APS)
Date: 22-09-2020
Publisher: IOP Publishing
Date: 28-12-2011
Publisher: American Physical Society (APS)
Date: 19-01-2022
Publisher: Springer Science and Business Media LLC
Date: 02-12-2021
DOI: 10.1038/S42005-021-00761-7
Abstract: Topological spin textures can serve as non-volatile information carriers. Here we study the current-induced dynamics of an isolated magnetic skyrmion on a nanoscale square-grid pinning pattern formed by orthogonal defect lines with reduced magnetic anisotropy. The skyrmion on the square grid can be pixelated with a quantized size of the grid. We demonstrate that the position, size, and shape of skyrmion on the square grid are electrically configurable. The skyrmion center is quantized to be on the grid and the skyrmion may show a hopping motion instead of a continuous motion. We find that the skyrmion Hall effect can be perfectly prohibited due to the pinning effect of the grid. The pixelated skyrmion can be harnessed to build future programmable racetrack memory, multistate memory, and logic computing device. Our results will be a basis for digital information storage and computation based on pixelated topological spin textures on artificial pinning patterns.
Publisher: AIP Publishing
Date: 04-01-2021
DOI: 10.1063/5.0034997
Abstract: The antiferromagnetic domain wall dynamics is currently a hot topic in mesoscopic magnetic systems. In this work, it is found that, based on the Thiele approach, the motion of an antiferromagnetic domain wall is described by the Duffing equation. Numerical simulations demonstrate that the antiferromagnetic domain wall can be used as a Duffing oscillator, and the transition between the periodic and chaotic motion can be used to detect the periodic signal in the presence of the white noise. Furthermore, we calculate the bifurcation diagram and Lyapunov exponents to study the chaotic behavior of an antiferromagnetic domain wall. The numerical simulations are in good agreement with the analytical solutions. Our results may be useful for building spintronic detection devices based on antiferromagnetic domain walls.
Publisher: Springer Science and Business Media LLC
Date: 26-12-2017
DOI: 10.1038/NPHYS4000
Publisher: AIP Publishing
Date: 24-02-2012
DOI: 10.1063/1.3672847
Abstract: We study the thermoelectric properties of three-dimensional topological insulators in magnetic fields with many holes (or pores) in the bulk. We find that at a high density of these holes in the transport direction the thermoelectric figure of merit, ZT, can be large due to the contribution of the topologically protected conducting surfaces and the suppressed phonon thermal conductivity. By applying an external magnetic field, a subgap can be induced in the surface states’ spectrum. We show that the thermoelectric efficiency can be controlled by this tunable subgap leading to values of ZT much greater than 1. Such high values of ZT for reasonable system parameters and its tunability by a magnetic field make this system a strong candidate for applications in the heat management of nanodevices, especially at low temperatures.
Publisher: Elsevier BV
Date: 04-2019
Publisher: American Physical Society (APS)
Date: 07-05-2021
Publisher: American Physical Society (APS)
Date: 22-05-2007
Publisher: American Physical Society (APS)
Date: 11-01-2005
Publisher: American Physical Society (APS)
Date: 30-09-2013
Publisher: American Chemical Society (ACS)
Date: 02-06-2022
Publisher: American Physical Society (APS)
Date: 16-08-2011
Publisher: AIP Publishing
Date: 02-2021
DOI: 10.1063/5.0034396
Abstract: We show a topological spin texture called “bimeronium” in magnets with in-plane magnetization. It is a topological counterpart of skyrmionium in perpendicularly magnetized magnets and can be seen as a combination of two bimerons with opposite topological charges. We report the static structure and spin-orbit-torque-induced dynamics of an isolated bimeronium in a magnetic monolayer with frustrated exchange interactions. We study the anisotropy and magnetic field dependences of a static bimeronium. We also explore the bimeronium dynamics driven by the d ing-like spin-orbit torque. We find that the bimeronium shows steady rotation when the spin polarization direction is parallel to the easy axis. Moreover, we demonstrate the annihilation of the bimeronium when the spin polarization direction is perpendicular to the easy axis. Our results are useful for understanding the fundamental properties of bimeronium structures and may offer an approach to build bimeronium-based spintronic devices.
Publisher: American Physical Society (APS)
Date: 15-11-2010
Publisher: American Physical Society (APS)
Date: 28-03-2008
Publisher: American Physical Society (APS)
Date: 13-11-2019
Publisher: American Physical Society (APS)
Date: 03-2017
Publisher: American Chemical Society (ACS)
Date: 19-10-2022
DOI: 10.1021/ACS.NANOLETT.2C03106
Abstract: Skyrmions and bimerons are versatile topological spin textures that can be used as information bits for both classical and quantum computing. The transformation between isolated skyrmions and bimerons is an essential operation for computing architecture based on multiple different topological bits. Here we report the creation of isolated skyrmions and their subsequent transformation to bimerons by harnessing the electric current-induced Oersted field and temperature-induced perpendicular magnetic anisotropy variation. The transformation between skyrmions and bimerons is reversible, which is controlled by the current litude and scanning direction. Both skyrmions and bimerons can be created in the same system through the skyrmion-bimeron transformation and magnetization switching. Deformed skyrmion bubbles and chiral labyrinth domains are found as nontrivial intermediate transition states. Our results may provide a unique way for building advanced information-processing devices using different types of topological spin textures in the same system.
Publisher: American Physical Society (APS)
Date: 17-08-2017
Publisher: American Physical Society (APS)
Date: 26-04-2005
Publisher: American Physical Society (APS)
Date: 03-2006
Publisher: AIP Publishing
Date: 27-01-2014
DOI: 10.1063/1.4863084
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-07-2019
Abstract: The observation of an antisymmetric magnetoresistance in a trilayer van der Waals heterostructure Fe 3 GeTe 2 /graphite/Fe 3 GeTe 2 .
Publisher: American Physical Society (APS)
Date: 24-02-2016
Publisher: AIP Publishing
Date: 09-08-2021
DOI: 10.1063/5.0056259
Abstract: Antiferromagnets are promising materials for future spintronic applications due to their unique properties including zero stray fields, robustness vs external magnetic fields, and ultrafast dynamics, which have attracted extensive interest in recent years. In this work, we investigate the dynamics of isolated skyrmions in an antiferromagnetic nanotrack with a voltage-gated region. It is found that the skyrmion can be jointly controlled by the driving current and the voltage-controlled magnetic anisotropy gradient. We further propose a design of logic computing gates based on the manipulation of antiferromagnetic skyrmions, which is numerically realized combining several interactions and phenomena, including the spin Hall effect, voltage-controlled magnetic anisotropy effect, skyrmion–skyrmion interaction, and skyrmion–edge interaction. The proposed logic gates can perform the basic Boolean operations of the logic AND, OR, NOT, NAND, and NOR gates. Our results may have a great impact on fundamental physics and be useful for designing future nonvolatile logic computing devices with ultra-low energy consumption and ultra-high storage density.
Publisher: American Physical Society (APS)
Date: 14-11-2022
Publisher: American Chemical Society (ACS)
Date: 31-07-2023
Publisher: Springer Science and Business Media LLC
Date: 17-07-2020
DOI: 10.1038/S41427-020-0232-9
Abstract: To stabilize nontrivial spin textures, e.g., skyrmions or chiral domain walls in ultrathin magnetic films, an additional degree of freedom, such as the interfacial Dzyaloshinskii–Moriya interaction (IDMI), must be induced by the strong spin-orbit coupling (SOC) of a stacked heavy metal layer. However, advanced approaches to simultaneously control the IDMI and perpendicular magnetic anisotropy (PMA) are needed for future spin-orbitronic device implementations. Here, we show the effect of atomic-scale surface modulation on the magnetic properties and IDMI in ultrathin films composed of 5d heavy metal/ferromagnet/ 4d(5d) heavy metal or oxide interfaces, such as Pt/CoFeSiB/Ru, Pt/CoFeSiB/Ta, and Pt/CoFeSiB/MgO. The maximum IDMI value corresponds to the correlated roughness of the bottom and top interfaces of the ferromagnetic layer. The proposed approach for significant enhancement of PMA and the IDMI through interface roughness engineering at the atomic scale offers a powerful tool for the development of spin-orbitronic devices with precise and reliable controllability of their functionality.
Publisher: American Physical Society (APS)
Date: 14-11-2016
Publisher: American Physical Society (APS)
Date: 07-04-2016
Publisher: Springer Science and Business Media LLC
Date: 08-05-2023
DOI: 10.1038/S41565-023-01386-3
Abstract: Topologically protected magnetic textures are promising candidates for information carriers in future memory devices, as they can be efficiently propelled at very high velocities using current-induced spin torques. These textures—nanoscale whirls in the magnetic order—include skyrmions, half-skyrmions (merons) and their antiparticles. Antiferromagnets have been shown to host versions of these textures that have high potential for terahertz dynamics, deflection-free motion and improved size scaling due to the absence of stray field. Here we show that topological spin textures, merons and antimerons, can be generated at room temperature and reversibly moved using electrical pulses in thin-film CuMnAs, a semimetallic antiferromagnet that is a testbed system for spintronic applications. The merons and antimerons are localized on 180° domain walls, and move in the direction of the current pulses. The electrical generation and manipulation of antiferromagnetic merons is a crucial step towards realizing the full potential of antiferromagnetic thin films as active components in high-density, high-speed magnetic memory devices.
Publisher: American Physical Society (APS)
Date: 11-07-2017
Publisher: American Physical Society (APS)
Date: 27-04-2020
Publisher: AIP Publishing
Date: 12-09-2011
DOI: 10.1063/1.3637055
Abstract: We study the thermoelectric properties of three-dimensional topological insulators with many holes (or pores) in the bulk. We show that at high density of these holes, the thermoelectric figure of merit, ZT, can be large due to the contribution of the conducting surfaces and the suppressed phonon thermal conductivity. The maximum efficiency can be tuned by an induced gap in the surface states dispersion through tunneling or external magnetic fields. The large values of ZT, much higher than unity for reasonable parameters, make this system a strong candidate for applications in heat management of nanodevices, especially at low temperatures.
Publisher: AIP Publishing
Date: 23-03-2011
DOI: 10.1063/1.3554202
Abstract: The current mediated domain-wall dynamics in a thin ferromagnetic wire is investigated. We derive the effective equations of motion of the domain wall. They are used to study the possibility to optimize the power supplied by electric current for the motion of domain walls in a nanowire. We show that a certain resonant time-dependent current moving a domain wall can significantly reduce the Joule heating in the wire, and thus it can lead to a novel proposal for the most energy efficient memory devices. We discuss how Gilbert d ing, nonadiabatic spin transfer torque, and the presence of Dzyaloshinskii–Moriya interaction can effect this power optimization.
Publisher: American Physical Society (APS)
Date: 25-02-2019
Publisher: American Physical Society (APS)
Date: 14-10-2008
Publisher: American Physical Society (APS)
Date: 18-03-2019
Publisher: American Physical Society (APS)
Date: 26-10-2020
Publisher: American Physical Society (APS)
Date: 24-10-2023
Publisher: American Physical Society (APS)
Date: 16-03-2007
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2015
Publisher: American Physical Society (APS)
Date: 30-10-2018
Publisher: American Physical Society (APS)
Date: 08-05-2017
Publisher: American Physical Society (APS)
Date: 23-01-2020
Publisher: AIP Publishing
Date: 16-08-2010
DOI: 10.1063/1.3481382
Abstract: We study the thermoelectric properties of three-dimensional topological Anderson insulators with line dislocations. We show that at high densities of dislocations the thermoelectric figure of merit ZT can be dominated by one-dimensional topologically protected conducting states channeled through the lattice screw dislocations in the topological insulator materials with a nonzero time-reversal-invariant momentum such as Bi0.9Sb0.1. When the chemical potential does not exceed much the mobility edge the ZT at room temperatures can reach large values, much higher than unity for reasonable parameters, hence making this system a strong candidate for applications in heat management of nanodevices.
Publisher: American Physical Society (APS)
Date: 23-01-2007
Publisher: Springer Science and Business Media LLC
Date: 11-11-2020
DOI: 10.1038/S41467-020-19511-4
Abstract: The ability to represent information using an antiferromagnetic material is attractive for future antiferromagnetic spintronic devices. Previous studies have focussed on the utilization of antiferromagnetic materials with biaxial magnetic anisotropy for electrical manipulation. A practical realization of these antiferromagnetic devices is limited by the requirement of material-specific constraints. Here, we demonstrate current-induced switching in a polycrystalline PtMn/Pt metallic heterostructure. A comparison of electrical transport measurements in PtMn with and without the Pt layer, corroborated by x-ray imaging, reveals reversible switching of the thermally-stable antiferromagnetic Néel vector by spin-orbit torques. The presented results demonstrate the potential of polycrystalline metals for antiferromagnetic spintronics.
Start Date: 12-2020
End Date: 12-2024
Amount: $380,000.00
Funder: Australian Research Council
View Funded Activity