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Schreiber, F.*; Meer, H.*; Schmitt, C.*; Ramos, R.*; 齊藤 英治; Baldrati, L.*; Kl
ui, M.*
Physical Review Applied (Internet), 16(6), p.064023_1 - 064023_9, 2021/12
被引用回数：3 パーセンタイル：26.56(Physics, Applied)We analyze the complex impact of the local magnetic spin texture on the transverse Hall-type voltage in device structures utilized to measure magnetoresistance effects. We find a highly localized and asymmetric magnetic sensitivity in the eight-terminal geometries that are frequently used in current-induced switching experiments, for instance, to probe antiferromagnetic materials. Using current-induced switching of antiferromagnetic NiO/Pt as an example, we estimate the change in the spin Hall magnetoresistance signal associated with switching events based on the domain-switching patterns observed via direct imaging. This estimate correlates with the actual electrical data after subtraction of a nonmagnetic contribution. Here, the consistency of the correlation across three measurement geometries with fundamentally different switching patterns strongly indicates a magnetic origin of the measured and analyzed electrical signals.
大柳 洸一*; Gomez-Perez, J. M.*; Zhang, X.-P.*; 吉川 貴史*; Chen, Y.*; Sagasta, E.*; Chuvilin, A.*; Hueso, L. E.*; Golovach, V. N.*; Sebastian Bergeret, F.*; et al.
Physical Review B, 104(13), p.134428_1 - 134428_14, 2021/10
被引用回数：13 パーセンタイル：78.56(Materials Science, Multidisciplinary)We report the observation of the spin Hall magnetoresistance (SMR) in a paramagnetic insulator. By measuring the transverse resistance in a Pt/Gd
Ga
O
(GGG) system at low temperatures, paramagnetic SMR is found to appear with an intensity that increases with the magnetic field aligning GGG's spins. The observed effect is well supported by a microscopic SMR theory, which provides the parameters governing the spin transport at the interface. Our findings clarify the mechanism of spin exchange at a Pt/GGG interface, and demonstrate tunable spin-transfer torque through the field-induced magnetization of GGG. In this regard, paramagnetic insulators offer a key property for future spintronic devices.
O/YIG structureQi, J.*; Hou, D.*; Chen, Y.*; 齊藤 英治; Jin, X.*
Journal of Magnetism and Magnetic Materials, 534, p.167980_1 - 167980_6, 2021/09
被引用回数：1 パーセンタイル：7.51(Materials Science, Multidisciplinary)Temperature dependence of the spin Hall magnetoresistance (SMR) has been investigated herein Pt/CrO/YFeO structure. Well below the N
el temperature of CrO, the SMR is not observed at the noise level of 1.2 ppm. In vicinity of the Nel temperature, only a positive SMR tracks the YIG magnetic switching process, supporting that the SMR of normal metal/antiferromagnetic insulator/ferromagnetic insulator trilayer is controlled by the Nel vector of the antiferromagnetic insulator. A high field magnetoresistance is observed up to an external magnetic field of 20000 Oe which has a field angle dependence symmetry consistent with the SMR. We attribute this high field magnetoresistance to be induced by the Hanle magnetoresistance in Pt.
Baldrati, L.*; Schmitt, C.*; Gomonay, O.*; Lebrun, R.*; Ramos, R.*; 齊藤 英治; Sinova, J.*; Klui, M.*
Physical Review Letters, 125(7), p.077201_1 - 077201_6, 2020/08
被引用回数：36 パーセンタイル：91.52(Physics, Multidisciplinary)We achieve current-induced switching in collinear insulating antiferromagnetic CoO/Pt, with fourfold in-plane magnetic anisotropy. This is measured electrically by spin Hall magnetoresistance and confirmed by the magnetic field-induced spin-flop transition of the CoO layer. By applying current pulses and magnetic fields, we quantify the efficiency of the acting current-induced torques and estimate a current-field equivalence ratio of 
TA
m
. The Nel vector final state 
is in line with a thermomagnetoelastic switching mechanism for a negative magnetoelastic constant of the CoO.
Hou, D.*; Qiu, Z.*; 齊藤 英治
NPG Asia Materials, 11, p.35_1 - 35_6, 2019/07
被引用回数：40 パーセンタイル：84.4(Materials Science, Multidisciplinary)Spin transport is a key process in the operation of spin-based devices that has been the focus of spintronics research for the last two decades. Conductive materials, such as semiconductors and metals, in which the spin transport relies on electron diffusion, have been employed as the channels for spin transport in most studies. Due to the absence of conduction electrons, the potential to be a spin channel has long been neglected for insulators. However, since the demonstration of spin transmission through a ferromagnetic insulator, it was realized that insulators with magnetic ordering can also serve as channels for spin transport. Here, the recent progress of spin transport in antiferromagnetic insulators is briefly described with an introduction to the experimental techniques. The observations regarding the temperature dependence of spin transmission, spin current switching and the negative spin Hall magnetoresistance are discussed. We also include the challenges for developing the functionality of antiferromagnetic insulators as well as the unresolved problems from the experimental observations.
-FeO/NiO/Pt epitaxial stacksDong, B.-W.*; Baldrati, L.*; Schneider, C.*; 新関 友彦*; Ramos, R.*; Ross, A.*; Cramer, J.*; 齊藤 英治; Klui, M.*
Applied Physics Letters, 114(10), p.102405_1 - 102405_5, 2019/03
被引用回数：11 パーセンタイル：52.56(Physics, Applied)We study the spin Hall magnetoresistance (SMR) in epitaxial -FeO/NiO(001)/Pt stacks, as a function of temperature and thickness of the antiferromagnetic insulating NiO layer. Upon increasing the thickness of NiO from 0 nm to 10 nm, we detect a sign change of the SMR in the temperature range between 10 K and 280 K. This temperature dependence of the SMR in our stacks is different compared to that of previously studied yttrium iron garnet/NiO/Pt, as we do not find any peak or sign change as a function of temperature. We explain our data by a combination of spin current reflection from both the NiO/Pt and -FeO/NiO interfaces and the thickness-dependent exchange coupling mode between the NiO and -FeO layers, comprising parallel alignment for thin NiO and perpendicular alignment for thick NiO.
