Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session PP03: V: Spin Transport and Magnetization DynamicsFocus
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Sponsoring Units: GMAG Chair: Josep Ingla Aynes, Technische Universiteit Delft Room: Virtual Room 3 |
Tuesday, March 21, 2023 9:00AM - 9:36AM |
PP03.00001: Ferroelectric control of the conversion between spin and charge currents Invited Speaker: Laurent Vila While spintronics has traditionally relied on ferromagnetic metals as spin generators and detectors, efficient spin-charge interconversion enabled by spin-orbit coupling in non-magnetic systems has drawn considerable interest in recent years in a new field called spinorbitronics. We report a new approach to generate and detect spin currents by exploiting the interplay between spin-orbit effects and ferroelectricity, in two classes of materials: two-Dimensional Electron Gases (2DEGS) appearing at oxides surfaces or interfaces [1], and ferroelectric Rashba semiconductors [2]. |
Tuesday, March 21, 2023 9:36AM - 9:48AM |
PP03.00002: Orbital magnetism in ultrathin films of CoFeB and its control by spin current Sergei Ivanov, Vladislav E Demidov, Sergej O Demokritov, Sergei Urazhdin We present experimental evidence for orbital magnetism in ultrathin films of amorphous ferromagnet Co40Fe40B20. Magnetoelectronic measurements based on the anomalous Hall effect (AHE) show a significant nonlinear contribution separate from the usual paramagnetic response, characterized by a different dependence on temperature and an opposite sign of AHE. A similar nonlinear feature is observed in current-biased microstructures in the ferromagnetic state. Brillouin Light Spectroscopy of thermal magnetization fluctuations reveals a strong current dependence of the Lande g-factor and the magnetic anisotropy on current, consistent with a large current-dependent orbital moment. We utilize a Hubbard model complemented with a two-order-parameter Landau theory of phase transition to demonstrate that the observed anomalous behaviors can be explained by the ferromagnetic orbital correlations associated with orbitally selective electron hopping confined to the film plane. This mechanism allows for efficient control of magnetic and magnetoelectronic properties of thin films via electron correlations. |
Tuesday, March 21, 2023 9:48AM - 10:00AM |
PP03.00003: Giant orbital Hall effect and orbital-to-spin conversion in 3d, 5d, and 4f metallic heterostructures Giacomo Sala, Pietro Gambardella Recent theories and experiments have shown that the spin Hall effect (SHE) produced by an electric current in transition-metal elements is accompanied by an orbital Hall effect (OHE) [1-3]. The induced spins and orbitals can exert spin and orbital torques, respectively, on the magnetization of an adjacent ferromagnet. Despite the expected large orbital generation, however, only a weak orbital torque has been reported so far. |
Tuesday, March 21, 2023 10:00AM - 10:12AM |
PP03.00004: Type-II quantum spin Hall effect in two-dimensional metals Richard A Klemm, Aiying Zhao, Qiang Gu, Timothy J Haugan, Thomas J Bullard An experiment is proposed to measure the Type-II quantum spin Hall effect of an electron or hole in a two-dimensional (2D) metal. A long cylindrical solenoid lies normally through the inner radius of a 2D metallic Corbino disk. The currect Is surrounding the solenoid produces an azimuthal magnetic vector potential but no magnetic field in the disk. In addition, a radial electric field is generated across the disk by imposing either (1) a potential difference Δv or (2) a radial charge current I across its inner and outer radii. Combined changes in Is and in either Δv or I generate spontaneously quantized azimuthal charge and spin currents. The experiment is designed to measure these quantized azimuthal charge and spin currents in the disk consistently. The quantum Hamiltonians for experiments (1) and (2) are both solved exactly. A method to control the Joule heating is presented, which could potentially allow the Type-II quantum spin Hall measurements to be made at room temperature. |
Tuesday, March 21, 2023 10:12AM - 10:24AM |
PP03.00005: Tuning the Hall response of a non-collinear antiferromagnet with spin-transfer torques and oscillating magnetic fields Oleg A Tretiakov, Sayak Dasgupta The kagome lattice antiferromagnets Mn3X(= Sn, Ge) have a non-collinear 120° ordered ground state, which engenders a strong anomalous Hall response. It has been shown that this response is linked to the magnetic order and can be manipulated through it. Here we use a combination of strain and spin-transfer torques to control the magnetic order and hence switch deterministically between states of different chirality. Each of these chiral ground states has an anomalous Hall conductivity tensor in a different direction. Furthermore, we show that a similar manipulation of the strained sample can be obtained through oscillating magnetic fields, potentially opening a pathway to optical switching in these materials. |
Tuesday, March 21, 2023 10:24AM - 10:36AM |
PP03.00006: Even-odd effect for spin current through thin antiferromagnetic insulator Niklas Rohling, Roberto E Troncoso We theoretically study spin transport in a nonmagnetic metal-antiferromagnetic insulator (AFI)-ferromagnetic insulator (FI) system. Specifically, we consider a thin NiO layer oriented in (111) direction sandwiched between and coupled by exchange interaction to the metal and the FI. The preferred magnetic orientation in the NiO are ferromagnetically ordered planes parallel to the interfaces to the metal and the FI. These planes are antiferromagetically stacked on each other. Furthermore, the magnetic orientation in the FI is pinning the magnetic orientation of the neighboring NiO plane. As a consequence, the orientation of the NiO plane next to the metal depends on whether the number of planes in the NiO layer is even or odd. Furthermore, this determines the sign of the spin current through the insulator-metal interface generated by a thermal gradient (spin Seebeck effect). We compute the spin current in this scenario for clean interfaces and neglecting magnon decay and find that with increasing temperatures, the NiO thickness dependence of the spin current is vanishing except the mentioned even-odd effect. The reason for this lies in the nature of the magnonic eigenstates of the AFI-FI system yielding a normalization condition for their amplitudes next to the metal which are crucial for the spin current. |
Tuesday, March 21, 2023 10:36AM - 10:48AM |
PP03.00007: Spin pumping in noncollinear antiferromagnets Mike A Lund, Kjetil Hals, Akshaykumar Salimath The spin pumping and spin-transfer torque (STT) mechanisms in antiferromagnets have been theoretically and experimentally investigated in recent years. However, most of these works have concentrated on collinear antiferromagnets, leaving the spin dynamics of the more complex noncollinear antiferromagnets largely unexplored. In this talk, I will present our latest work [1] on ac spin pumping in non-collinear antiferromagnets. Starting from an effective theory of the spin system, we derive the Onsager coefficients connecting the spin pumping and STT associated with the dynamics of the SO(3)-valued antiferromagnetic order parameter. Our theory is applied to a kagome AFM resonantly driven by a uniform external magnetic field. We demonstrate that the reactive (dissipative) STT parameter can be extracted from the pumped ac spin-current in phase (in quadrature) with the driving field. Furthermore, we find that the three spin-wave bands of the kagome AFM generate spin currents with mutually orthogonal polarization directions. This offers a unique way of controlling the spin orientation of the pumped spin current by exciting different spin-wave modes. |
Tuesday, March 21, 2023 10:48AM - 11:00AM Author not Attending |
PP03.00008: Ultrafast generation of nonthermal magnons in antiferromagnetic systems Alireza Qaiumzadeh, Marion Barbeau, Mikhail Titov, Mikhail Katsnelson We describe a nonthermal magnon activation mechanism in antiferromagnetic (AFM) systems via hot electrons excited by an ultrafast intense laser pulse. We employ a quantum kinetic equation that takes into account a direct electron-magnon scattering channel in either bulk AFM metal or at the interface of the AFM/normal-metal heterostructure. The mechanism is responsible for the nonequilibrium population of AFM magnon modes on a subnanosecond timescale, which are formed shortly after the local thermalization of hot electrons by Coulomb interactions. Nonequilibrium magnon populations can be manipulated by applying an external magnetic field. Our work paves the way toward spin dynamics control in AFM systems via the ultrafast manipulation of out-of-equilibrium magnon excitations. |
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