Bulletin of the American Physical Society
APS March Meeting 2024
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session S62: Spin-Dependent Transport |
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Sponsoring Units: GMAG Chair: Yang Zhang, IAMM HQ, University of Tennessee Knoxville Room: 208CD |
Thursday, March 7, 2024 8:00AM - 8:12AM |
S62.00001: Manipulating chiral-spin transport with ferroelectric polarization Xiaoxi Huang, Xianzhe Chen, Yuhang Li, John M Mangeri, Hongrui Zhang, Maya Ramesh, Hossein Taghinejad, Peter Meisenheimer, Lucas Caretta, Sandhya Susarla, Rakshit Jain, Tianye Wang, Cheng-Hsiang Hsu, Isaac A Harris, Sajid Husain, Hao Pan, Ziqiang Qiu, Darrell G Schlom, Daniel C Ralph, Jorge Iñiguez, Ran Cheng, Zhi (Jackie) Yao, Ramamoorthy Ramesh Intense studies on spin transport in magnetic insulators have triggered renewed interest in magnon physics, and the potential use of magnons in energy-efficient electronics. Magnon flow in magnetic insulators, however, has thus far been manipulated primarily by magnetic fields that are expensive in energy. Here we report the experimental observation electric-field control of magnon transport in multiferroic BiFeO3, where the magnon transport is modulated in a non-volatile way by the ferroelectric polarization. The flow of magnons through a BiFeO3 layer changes by 18% at room temperature depending on the direction of the ferroelectric polarization, as measured by the inverse spin Hall technique. The spin torque borne by these magnons is furthermore sufficient to switch the magnetization of an adjacent ferromagnetic layer, with the critical switching current density similarly dependent on the ferroelectric polarization. Utilizing such a ferroelectrically controllable magnon transmission in BiFeO3, we propose an all oxide, energy-scalable logic that is composed of spin-orbit injection, detection, and magnetoelectric control. |
Thursday, March 7, 2024 8:12AM - 8:24AM |
S62.00002: Uniaxial magnon spin transport in electric field controlled chiral antiferromagnetic insulator Sajid Husain, Isaac A Harris, Peter Meisenheimer, Maya Ramesh, Hossein Taghinejad, Pravin Kavle, Lucas M Caretta, Paul Stevenson, James G Analytis, Darrell G Schlom, Sayeef Salahuddin, Lane W Martin, Zhi (Jackie) Yao, Ramamoorthy Ramesh Magnons, elementary excitations of the magnetic order, have been manifested as ultralow energy information carriers for future technological applications such as magneto-electric spin orbit coupled logic. Bismuth ferrite (BiFeO3, BFO) is the only insulating antiferromagnet that exhibits multiple order parameters and has been demonstrated to be useful for electric field manipulation of the magnetic order [1], as well as control of magnon transport [2]. The coercive electric field in BFO, however, is large, limiting its practical usefulness. La-substitution (LBFO) has been proposed to mitigate this challenge [3], yet the effects of La-substitution on the local magnetic properties are not well understood. In this work, we experimentally demonstrate the antiferromagnetic non-local magnon spin transport in LBFO and detected via inverse spin Hall effect of Pt. While BFO exhibits well defined ferroelectric domains, LBFO has mixed ferroelectric and antiferroelectric phases and, using electrical field pulses, single ferroelectric domains can be formed. This implies the formation of single magnetic domains, which are extremely attractive for magnonic devices. We hypothesize that this is due to the 12 possible ferroelectric switching paths in LBFO, whereas only 4 possible directions exist in BFO [3]. This uniform magnetic state in a single ferroelectric domain leads to efficient spin transport, due to reduced domain wall scattering, contrary to multidomain BFO. The observed non-local magnons are highly anisotropic in-plane with respect to substrate crystallographic directions, independent of antiferromagnetic layer thickness. This observation of switchable, efficient magnon transport in LBFO is an important milestone for realizing antiferromagnetic magnons in future applications. |
Thursday, March 7, 2024 8:24AM - 8:36AM |
S62.00003: Low temperature spin Seebeck effect in non-magnetic VO2 thin film Renjie Luo, Liyang Chen, Tanner Legvold, Henry Navarro, ALI C BASARAN, Deshun Hong, Changjiang Liu, ANAND BHATTACHARYA, IVAN K SCHULLER, Douglas Natelson The spin Seebeck effect (SSE) involves the generation of spin current in the presence of a heat flow across a magnetically active material. SSE in paramagnets is considerably less studied, and the mechanism of paramagnetic SSE is still unclear. Here we present a systematic study of the longitudinal SSE (LSSE) in insulating VO2 film at low temperatures. The LSSE grows linearly with increasing field at low fields but experiences a field-induced reduction at high fields and the lowest temperatures, qualitatively consistent with the recent model of paramagnetic SSE response. The LSSE shows the expected angular dependence with the in-plane field orientation and is linear in the heating power. The sign of the LSSE response is not consistent with that expected for a triplon-dominated SSE. Finally, we will show how thickness of VO2 film influences the temperature dependence of LSSE magnitude. |
Thursday, March 7, 2024 8:36AM - 8:48AM |
S62.00004: Spin Seebeck effect in quasi-2D antiferromagnet BaNi2V2O8 with signatures of the Berezinskii-Kosterlitz-Thouless transition Kurea Nakagawa, Minoru Kanega, Tomoyuki Yokouchi, Masahiro Sato, Yuki Shiomi The spin Seebeck effect (SSE) is useful for elucidating spin excitation and transport of magnetic states. Among exotic magnetic states, two-dimensional (2D) spin systems, in which a quasi-long-range order emerges owing to enhanced spin fluctuations, are interesting because their spin transport remains unclear. In this study, we investigate the SSE in a quasi-2D antiferromagnet BaNi2V2O8. BaNi2V2O8 has been reported to exhibit Berezinskii-Kosterlitz-Thouless (BKT)-like behavior, highlighting its distinct 2D character and quasi-long-range order [1,2]. We experimentally found that SSE signals in Pt/BaNi2V2O8 decrease with increasing temperature and persist well above the Néel temperature. Our numerical calculations showed that the observed temperature dependence of the SSE signals is linked to the strong magnetic correlations in the BKT-like phase. |
Thursday, March 7, 2024 8:48AM - 9:00AM |
S62.00005: Giant Magnetothermal Conductivity Switching in WSi2 Single Crystals Across a Broad Temperature Range Jackson E Hise, Joseph P Heremans, Joshua E Goldberger, Karl Koster The ability to mitigate the flow of heat in a material through external stimuli, such as a magnetic or electric field, allow for the construction of solid-state heat switches to be used in a variety of applications in heat management, power generation and cooling.1 In the proposed talk, we will present evidence of high purity ⍺-WSi2 single crystal’s possession of a large magnetoresistance impacting thermal conductivity at temperatures below 100K. It also was found that at temperatures below 20K, the thermal conductivity switching ratio is >6 when under a magnetic field between 0T and 9T due to the depreciation of electron phonon scattering rates and with an experimental magnetoresistance of 2200-3500% generated through electron-hole compensation. Our measurements produced values for thermal conductivity and electrical conductivity which align with the theoretical approximation of the Lorenz number, as well as a finding that a 5-mm sample yields a thermal conduction switching speed of from 1 x 10-4 seconds at 5K to 0.2 seconds at 100K. The magnitude of high purity ⍺-WSi2 single crystal’s performance in both magnetoresistance and switching ratio supports the material be implemented as a thermal regulator in a solid-state heat switch. |
Thursday, March 7, 2024 9:00AM - 9:12AM |
S62.00006: On the asymmetry of the magnonic Hanle effect in antiferromagnets Eric Kleinherbers, Yaroslav Tserkovnyak In the magnonic Hanle effect, which has been discovered only recently [Wimmer et al., PRL 125, 247204 (2020)], a spin current is injected into an insulating antiferromagnet (hematite) and tuned by means of an applied magnetic field. We present a theoretical framework to describe the spin transport in terms of low-energy waves of the antiferromagnetic Néel order --- the classical counter part of magnons. Intriguingly, these waves come with two different polarizations which we describe, in analogy to optics, using the Stokes vector on the Poincaré sphere. We find that the polarization changes periodically with a frequency that is nonlinear in the magnetic field leading to an asymmetry in the measured spin signal. By modelling the energy-dependent spin injection and assuming a diffusive transport regime, we are able to reproduce the signatures found in the experiment. |
Thursday, March 7, 2024 9:12AM - 9:24AM |
S62.00007: ac Hanle effect in spin valves Yaroslaw Bazaliy It is known [1] that ac spin current flowing through an FNF spin valve produces results reminiscent of Hanle effect, with current frequency playing the role of external magnetic field. We study the combination of the two effects: an ac Hanle effect in spin valves and find that it produces new types of signatures in voltage dependencies. |
Thursday, March 7, 2024 9:24AM - 9:36AM |
S62.00008: Tunneling Magnetoresistance in Magnetic Tunnel Junctions with a Single Ferromagnetic Electrode Kartik Samanta, Yuan-Yuan Jiang, Tula R. Paudel, Ding-Fu Shao, Evgeny Y Tsymbal Magnetic tunnel junctions (MTJs) are key components of magnetic random-access memories. Normally, they consist of two ferromagnetic (FM) electrodes separated by insulating barrier and exhibit a tunneling magnetoresistance (TMR) effect that is a change in MTJ’s resistance when magnetization of the two FM electrodes alters from parallel to antiparallel. Here, we demonstrate that TMR can occur in MTJs with a single FM electrode, provided that the counter electrode is an antiferromagnetic (AFM) metal that supports a spin-split band structure and/or a Néel spin current. Using RuO2 as a representative example of such antiferromagnet and CrO2 as a FM metal, we perform quantum-transport calculations and predict a giant TMR effect in all-rutile RuO2/TiO2/CrO2 MTJs. The calculated TMR ratio of about 1000% in the (110)-stacked MTJs stems from spin-dependent conduction channels in CrO2 (110) and RuO2 (110), whose matching alters with CrO2 magnetization orientation, while TMR in the (001)-stacked MTJs originates from the Néel spin currents and different effective TiO2 barrier thickness for the two magnetic sublattices. Our results demonstrate a possibility of a sizable TMR in MTJs with a single FM electrode and offer a practical test for using AFM RuO2 in functional spintronic devices. |
Thursday, March 7, 2024 9:36AM - 9:48AM |
S62.00009: Spin transport at a heavy metal/ferrimagnetic insulator interface above and below the Curie temperature Sauviz Alaei, Xin Yu Zheng, Sanyum Channa, Lerato Takana, Erin Fleck, Tian-Yue Chen, Andrew D Kent, Yuri Suzuki Spin wave spintronics are an attractive alternative to conventional electronics with potential for improved energy efficiency and processing speed. Practical implementation requires a low damping magnetic insulator allowing for coherent excitation and propagation of spin waves, typically generated using the spin Hall effect of an adjacent metal. One candidate is the recently developed thin film lithium aluminum ferrite (LAFO)[1]. In this work, we demonstrate spin transport at a Ta/LAFO interface probed via the spin Hall magnetoresistance (SHMR). Tantalum films 2-20 nm thick were sputtered onto 4 nm LAFO films; at this LAFO thickness, the Ta/LAFO Curie temperature is below 300 K, suppressed from that of single layer LAFO films. The SHMR contribution to the resistivity was determined by measuring the angle-dependent magnetoresistance (ADMR) in a saturating magnetic field. From the Ta thickness dependence of the SHMR we extract a spin diffusion length of ~1 nm and spin Hall angle of ~0.05 in Ta as well as a spin mixing conductance of ~1014 Ω -1 m-2 at the Ta/LAFO interface. The ADMR is consistent above and below the Ta/LAFO Curie temperature and is similar to that of other systems associated with efficient spin transport. |
Thursday, March 7, 2024 9:48AM - 10:00AM |
S62.00010: Growth and Antiferromagnetic Properties of Epitaxial RuO2 Thin Films Owen Ericksen, Chang-Beom Eom, Mark S Rzchowski Recent studies of RuO2 have challenged the previously accepted characterization of it as a Pauli paramagnet, suggesting antiferromagnetic ordering in both bulk and thin-film samples. The rutile structure of RuO2, in conjunction with its magnetic ordering, breaks PT symmetry (alter-magnetism), making it an intriguing candidate for antiferromagnetic spintronics. However, the existence of magnetic domains complicates the understanding, and presents challenges for spintronic applications. |
Thursday, March 7, 2024 10:00AM - 10:12AM |
S62.00011: Observation of giant topological Hall effect in Pt/NiCo2O4 heterostructure over wide temperature range Bharat Giri, Xiaoshan Xu The spin configuration of materials significantly influences their transport characteristics. To investigate the potential emergence of novel spin structure in heterostructure of strongly spin-orbit coupled metal Platinum (Pt) deposited on ferrimagnetic NiCo2O4 (NCO)/MgAl2O4 (001) films with perpendicular magnetic anisotropy (PMA)[1], we studied the spin transport properties at various temperature with different NCO thickness (8-30nm). In addition to the anomalous Hall effect expected from NCO, we observed topological Hall effects (THE) before the coercive field (HC). The magnitude of THE increases with increasing T and vanishes near transition temperature of NCO. These results indicate that interfacial Dzyaloshinskii Moriya interactions (iDMI) of NCO/Pt comes to play, and strong spin orbit coupling enhances the iDMI[2] and becomes influential to compete with exchange interaction to form skyrmions. Based on the measured THE, the maximum estimated skyrmion density is 103 at 270K for 16 nm thick NCO sample. |
Thursday, March 7, 2024 10:12AM - 10:24AM |
S62.00012: Detection of Anisotropy in LaFeO3/SrTiO3 Thin Films through use of Spin Hall Magnetoresistance Joseph A Lanier, Justin J Michel, Jose Flores, Fengyuan Yang The field of antiferromagnetic spintronics has gained popularity over the last decade, and many techniques have been developed to understand the behavior of the Néel vector in these materials. In this work we use spin-hall magnetoresistance measurments in order to probe the magnetism in a set of antiferromagnetic films. LaFeO3 is a g-type antiferromagnet with slight canting leading to a small net moment. LaFeO3 thin films of high crystalline quality were grown on SrTiO3(100) substrates by off-axis magnetron sputtering. Angular spin-hall magnetoresistance (SMR) measurements were carried out on ultrathin LaFeO3/Pt bilayers. The behavior of these films was then compared to that of bulk like films in order to understand the effect of the SrTiO3 interface. From the SMR we are able to better understand the anisotropy as well as potential switching behavior of these films. |
Thursday, March 7, 2024 10:24AM - 10:36AM |
S62.00013: Spin-charge conversion in 2D semimetals Peng Song As an all-electrical scheme to generate, detect and manipulate spin current, the spin Hall effect has been heavily investigated as a primary route toward next-generation spintronic devices. Traditional spin Hall materials are mostly based on heavy metals, like Pt, W and Ta, that have strong spin-orbit coupling. However, the high symmetry and dimensionality of these materials make the control and optimization of spin Hall effect a major obstacle toward device applications.1 Low-symmetry 2D semimetals have been emerging materials to study novel spin Hall effects and their control.2 In this talk, I will present our recent progress in this regard to generate and control novel spin-charge conversion in 2D semimetals. Through transport studies, we observed a novel spin Hall effect that can generate out-of-plane spin polarization due to symmetry breaking. Furthermore, using 2D semimetal as a spin Hall layer, we achieved electrostatic control of spin-charge conversion in a broad range, which is extremely difficult for heavy metals. Finally, I will discuss how we use van der Waals heterostructures of 2D semimetal and 2D ferromagnets to achieve highly efficient interface spin transport and eventually a spin readout signal that is two orders of magnitudes higher than conventional 3D structures. Our demonstrations prove the appealing potential of 2D spin Hall crystals as building block for highly efficient spintronic devices, including memory and logic devices. |
Thursday, March 7, 2024 10:36AM - 10:48AM |
S62.00014: First-principles calculations of orbital Hall and Nernst effects in monoatomic crystal to binary alloys and multilayers Kenji Nawa, Yushi Tsujide, Sonny H. Rhim, Masamitsu Hayashi, Michael Weinert, Kohji Nakamura Orbital Hall effect has attracted attention as a new degree of freedom in solid state in addition to the spin Hall effect [1,2]. Generation and controlling of orbital current offer highly-efficient magnetization switching in spin applications. In this work, intrinsic orbital Hall conductivity (OHC) and orbital Nernst conductivity (ONC), thermally-driven transport, in monoatomic crystal are investigated using first-principles full-potential linearized augmented plane wave method [3]. The systematic calculations of chemical trend (atomic element) for 40 elements in the periodic table clarified that the OHC is maximized near the middle of transition metals (TMs) with d electrons, which agrees with the earlier work [4]. For these d TMs, the OHC shows large value in wide energy region within the rigid band analysis, indicating the significant contribution of Berry curvature in not only localized d states but also itinerant p states. On the other hand, the ONC accompanies localized d states, especially near the d band edges in the density of states, and a large ONC is obtained in Ni (assumed to be nonmagnetic). We also discuss the results for binary alloys and multilayers in terms of atomic composition dependence and stacking effect. |
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