Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session A47: Proximity Effects and Spin Transport in Complex OxidesFocus
|
Hide Abstracts |
Sponsoring Units: GMAG DMP DCOMP Chair: Qian Li, University of California, Berkeley Room: 710/712 |
Monday, March 2, 2020 8:00AM - 8:12AM |
A47.00001: Low-temperature magnetic proximity effects in Mg(Al,Fe)2O4/Bi2Se3 bilayers Lauren Riddiford, Peng Li, Alexander Grutter, Yuri Suzuki Topological insulators (TIs) are of significant interest in spin current-based electronics due to their strong spin-orbit coupling from spin-momentum locking of surface states. Bi2Se3 is a 3D topological insulator with a semiconductor gap in the bulk and gapless surface states. However, conduction near room temperature is typically bulk-dominated due to Se vacancies. Bilayers of Mg(Al,Fe)2O4 (MAFO), a magnetic insulator, and Bi2Se3 show highly efficient spin pumping in the bulk-dominated regime at room temperature. At low temperature, below 45 K, we have found evidence of proximity-induced magnetism in the TI. To understand the underlying mechanism of this proximity-induced magnetism, we performed polarized neutron reflectometry which indicates a sharp interface and a magnetic moment in the TI up to at least 45 K. In transport measurements, we observed both the anomalous Hall effect (AHE) and a large unidirectional magnetoresistance in the TI. The AHE, around 1 Ω at 2 K, was observed up to ~40 K and was amplified by electrically gating Bi2Se3. These results suggest that the induced magnetism in Bi2Se3 is primarily due to the coupling between MAFO and the surface states of Bi2Se3. |
Monday, March 2, 2020 8:12AM - 8:24AM |
A47.00002: Exotic coupling in garnet-ferromagnet heterostructures Patrick Quarterman, Yabin Fan, Luqiao Liu, Alexander Grutter Metallic and insulating ferromagnets (FM) have been extensively studied for use in spintronic like structures—the former for spin transfer and spin orbit torques and the latter for generation of magnon spin currents [1,2]. Recently, we have shown that in yttrium iron garnet (YIG)/permalloy (Py) bilayers, grown on Si, the YIG preferentially aligns antiparallel to the Py at low field and can be used to form a magnon spin valve [3]. However, the observed coupling in YIG/FM is quite complex and is heavily dependent on the sample geometry—for example when the same bilayers are grown on Gd3Ga5O12 (GGG) substrates, no antiparallel coupling has been observed. In this work, we discuss the coupling of YIG to Py and Co when grown on Si and GGG substrates by measuring the magnetic depth profile using polarized neutron reflectometry. The effect of texture and choice of FM on coupling to the underlying YIG layer will be presented in detail. |
Monday, March 2, 2020 8:24AM - 8:36AM |
A47.00003: Angle-dependent magnetoresistance of Pt/EuO1-x thin films Narendra Shrestha, Joseph R Murphy, Subash Kattel, WIlliam Rice, Jinke Tang Europium monoxide (EuO) has attracted a great deal of attention in spintronic research due to its unique ferromagnetic and semiconducting properties. Here, we have prepared Pt/EuO thin films by pulsed laser deposition. We study the magnetic and transport properties as a function of temperature and field. The magnetic data shows enhanced Curie temperature to 140 K, which is a signature of oxygen deficiency. Transport measurements reveal a metal-insulator transition below 70 K associated with the ferromagnetic ordering of EuO. Angle-dependent magnetoresistance exhibits behavior that cannot be explained solely on the basis of anisotropic magnetoresistance of EuO: rather, the MR shows a strong angular dependence as the magnetic field, H, is rotated from in-plane to perpendicular-to-plane, while keeping H perpendicular to the current – a feature consistent with spin Hall magnetoresistance. We discuss the possible origins of the angular dependence by considering the strong spin-orbit coupling present in the system, magnetic proximity effect, interface properties, and the hetero-structure nature of the films. |
Monday, March 2, 2020 8:36AM - 8:48AM |
A47.00004: Magnetoresistance and second harmonic Hall measurement of Pt/CoFe2O4 bilayers Zexuan Zhang, Phillip Dang, Joseph Casamento, Xiang Li, Yongjian Tang, Tianxiang Nan, Daniel C. Ralph, Huili Xing, Debdeep Jena CoFe2O4 (CFO), a room temperature ferrimagnetic insulating spinel ferrite, is a promising candidate for energy efficient spintronics. Magnetic proximity effect was believed to be absent in Pt/CFO bilayers grown by sputtering or pulsed laser deposition (PLD), but was recently observed in Pt/CFO (001) bilayers grown entirely by molecular beam epitaxy (MBE) [Amamou, Walid et al. Physical Review Materials 2, 011401 (2018)]. Here, we report the observation of magnetic proximity effect in ex situ sputtered Pt on MBE grown CFO (001) at room temperature. Angle dependent magnetoresistance measurements in the direction insensitive to spin Hall magnetoresistance (SMR) indicates that magnetic proximity effect is a relatively robust phenomenon. We also studied high quality CFO (111) on multiferroic LuFeO3 (111) using MBE, since the impact of crystal orientation of CFO on magnetic interaction has been reported to be significant between Pt and CFO. In the same Pt/CFO (001) and Pt/CFO (001) stacks we also carried out the second harmonic Hall measurement and found Nernst effect dominating the signal. |
Monday, March 2, 2020 8:48AM - 9:00AM |
A47.00005: Hydroxide-based Magneto-ionics Alberto Quintana-Puebla, Abigail A. Firme, Christopher J Jensen, Kai Liu Recently, magneto-ionics has attracted a lot of interests where controlled motion of ions, e.g., under an electric field, is employed to modify metal/oxide interfaces and their magnetic responses in a reversible and non-volatile fashion. Despite the promising initial oxygen-based magneto-ionic systems, it has been demonstrated that hydrogen-based system showed better performance. |
Monday, March 2, 2020 9:00AM - 9:12AM |
A47.00006: Current-induced magnetization switching in all-oxide heterostructures Liang Liu, Qing Qin, Weinan Lin, Changjian LI, Qidong Xie, Shikun He, Xinyu Shu, Chenghang Zhou, Zhishiuh Lim, Jihang Yu, Wenlai Lu, Mengsha Li, Xiaobing Yan, Stephen J Pennycook, Jingsheng Chen The electrical switching of magnetization through spin-orbit torque (SOT) holds promise for application in information technologies. Materials with strong spin-orbit coupling, such as heavy metals can convert a charge current into a spin current. The spin current can then execute a transfer torque on the magnetization of a neighboring magnetic layer, usually a ferromagnetic metal like CoFeB, and reverse its magnetization. Here, we combine a ferromagnetic transition metal oxide with an oxide with strong spin-orbit coupling to demonstrate all-oxide SOT devices. We show current-induced magnetization switching in SrIrO3/SrRuO3 bilayer structures. By controlling the magnetocrystalline anisotropy of SrRuO3 on (001)- and (110)-oriented SrTiO3 (STO) substrates, we designed two types of SOT switching schemes. For the bilayer on the STO(001) substrate, a magnetic-field-free switching was achieved, which remained undisturbed even when the external magnetic field reached 100 mT. The charge-to-spin conversion efficiency for the bilayer on the STO(110) substrate ranged from 0.58 to 0.86, depending on the directionality of the current flow with respect to the crystalline symmetry. |
Monday, March 2, 2020 9:12AM - 9:24AM |
A47.00007: Enhancement of spin-charge interconversion efficiency by interface engineering in all oxide La0.3Sr0.7MnO3/SrIrO3 system Xiaoxi Huang, Hongrui Zhang, Shehrin Sayed, Shang-Lin Hsu, Arnoud Everhardt, Tanay Gosavi, Chia-Ching Lin, Sasikanth Manipatruni, Ian Young, Sayeef Salahuddin, Daniel Ralph, Ramamoorthy Ramesh
|
Monday, March 2, 2020 9:24AM - 9:36AM |
A47.00008: Magnetic properties of Manganite/Iridate bilayers Suzanne Te Velthuis, Stephan Rosenkranz, Xiao Wang, Javier Tornos, Fernando Gallego, David J Keavney, John William Freeland, Yongseong Choi, Joerg Strempfer, Daniel Haskel, Brian James Kirby, Timothy R Charlton, Jacobo Santamaria The relationship between spin-orbit coupling (SOC), emergent topological states, and spin Hall effects, which are highly relevant for spintronics, has driven the recent interest in materials with strong SOC. To probe the influence of SOC at 3d-5d complex oxide interfaces, we have investigated ferromagnetic La0.7Sr0.3MnO3/SrIrO3 bilayers deposited on SrTiO3. We find that depending on the growth order, the coercive field of the magnetization loop differs significantly at low temperatures. Similar to previous reports, a net moment on Ir has been recorded with element specific XMCD experiments, which is aligned antiparallel to the Mn moments within the manganite. We find that the Ir moment does not follow the same temperature dependence as the magnetization of the manganite, and is limited to the interface. The origins and implications of this result will be discussed. |
Monday, March 2, 2020 9:36AM - 10:12AM |
A47.00009: Current-manipulated propagation of spin waves in antiparallel coupled stripe domains of La 0.67 Sr 0.33 MnO 3 thin films Invited Speaker: Haiming Yu Spin waves may enable low-power devices based on spin information transmission that |
Monday, March 2, 2020 10:12AM - 10:24AM |
A47.00010: Anisotropic magnon spin diffusion length in ultra-thin spinel ferrite thin films Ruofan Li, Tianxiang Nan, Peng Li, Yuri Suzuki, Daniel Ralph Magnon-mediated spin transport in magnetically ordered insulators is of interest in the field of spintronics as it enables transport of spin information with ultra-low-dissipation. Long-distance spin transport has been demonstrated previously in low-damping iron garnets with the film thickness typically above 100 nm. For this large thickness, strain relaxation in the film impedes the study of strain control of magnons. Here we demonstrate anisotropic magnon spin transport in coherently-strained ultra-thin epitaxial films of magnesium aluminum ferrite (MgAl0.5Fe1.5O4, MAFO) with low Gilbert damping and thickness of 6 nm. Using nonlocal measurements with the spin polarization injected from Pt bars, we found a ~50 % enhancement of the magnon spin diffusion length for propagation in the [110] direction compared to [100], for both electrically and thermally excited magnons. We correlate this anisotropy to the biaxial magnetic anisotropy in MAFO induced by tetragonal distortion. Our finding suggests that epitaxial strain can be used to further engineer magnon spin transport. |
Monday, March 2, 2020 10:24AM - 10:36AM |
A47.00011: Low Magnetic Damping in Epitaxial Li0.5Fe2.5O4 Thin Films Xin Yu Zheng, Lauren Riddiford, Jacob Wisser, Yuri Suzuki One of the major challenges in the field of spin-current based electronics is the development of low-loss ferromagnetic insulators capable of generating spin currents without an accompanying charge current. Bulk phase Li0.5Fe2.5O4 (LFO) is known to have the lowest Gilbert damping parameter (α ≈ 0.002) among the spinel ferrites, but the growth of LFO thin films with desirable microwave properties has remained elusive due to the volatility of lithium. In this talk, we demonstrate the realization of epitaxial LFO ultra-thin films (~3nm) on MgAl2O4 substrates with an ultra-low damping of α ≈ 0.0005 and an FMR linewidth of 7.5 Oe at 15GHz. These values rival those of yttrium iron garnet (YIG), the gold standard of low-loss magnetic insulators. LFO also offers distinct advantages over YIG such as smaller external field requirements and thinner interfacial layers crucial for magnetic switching. Our results place LFO as an attractive new candidate for low-loss microwave materials in the field of spintronics. |
Monday, March 2, 2020 10:36AM - 10:48AM |
A47.00012: Interface ferromagnetism and anomalous Hall effect of CdO/ferromagnetic-insulator heterostructures Yang Ma The experimental observation of quantum anomalous Hall effect (QAHE) in magnetic topological insulators has stimulated enormous interest in condensed-matter physics and materials science. For the purpose of realizing high-temperature QAHE, several material candidates have been proposed, among which the interface states in the CdO/ferromagnetic insulator heterostructures are particularly interesting and favorable for technological applications. Here, we report the experimental observation of the interfacial ferromagnetism and anomalous Hall effect in the Fe3O4/CdO/Fe3O4 heterostructures grown via oxide molecular-beam epitaxy. Systematical variation of the CdO thickness reveals the interface ferromagnetism as the major cause for the observed planar magnetoresistance and anomalous Hall effect. Our results might pave the way to engineer oxide interface states for the exploration of QAHE towards exotic quantum-physical phenomena and potential applications. |
Monday, March 2, 2020 10:48AM - 11:00AM |
A47.00013: Structural, Magnetic and Electrical Transport Properties of YIG Thin Films with Heavily Reduced Oxygen Content Shu Mi, Venkata Swamy Gollapothu, Haoliang Huang, Yalin Lu, Yonggang Zhao Yttrium iron garnet (YIG) is very promising for spintronic devices due to its insulating nature, low damping and large magnon decay length. Moreover, YIG films have greatly facilitated the research on spin pumping, spin Seebeck effect and topological spintronics [1]. So far, many studies have shown that oxygen content is essential for tuning the structural and magnetic properties of YIG films [2]. But the effect was not so remarkable because only a small amount of oxygen content has been reduced. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700