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Register a new userNon-local magnetoresistance in YIG/Pt nanostructures
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We study the local and non-local magnetoresistance of thin Pt strips deposited onto yttrium iron garnet. The local magnetoresistive response, inferred from the voltage drop measured along one given Pt strip upon current-biasing it, shows the characteristic magnetization orientation dependence of the spin Hall magnetoresistance. We simultaneously also record the non-local voltage appearing along a second, electrically isolated, Pt strip, separated from the current carrying one by a gap of a few 100 nm. The corresponding non-local magnetoresistance exhibits the symmetry expected for a magnon spin accumulation-driven process, confirming the results recently put forward by Cornelissen et al. [1]. Our magnetotransport data, taken at a series of different temperatures as a function of magnetic field orientation, rotating the externally applied field in three mutually orthogonal planes, show that the mechanisms behind the spin Hall and the non-local magnetoresistance are qualitatively different. In particular, the non-local magnetoresistance vanishes at liquid Helium temperatures, while the spin Hall magnetoresistance prevails.
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We investigate the spin-current transport through antiferromagnetic insulator (AFMI) by means of the spin-Hall magnetoressitance (SMR) over a wide temperature range in Pt/NiO/Y$_3$Fe$_5$O$_{12}$ (Pt/NiO/YIG) heterostructures. By inserting the AFMI NiO layer, the SMR dramatically decreases by decreasing the temperature down to the antiferromagnetically ordered state of NiO, which implies that the AFM order prevents rather than promotes the spin-current transport. On the other hand, the magnetic proximity effect (MPE) on induced Pt moments by YIG, which entangles with the spin-Hall effect (SHE) in Pt, can be efficiently screened, and pure SMR can be derived by insertion of NiO. The dual roles of the NiO insertion including efficiently blocking the MPE and transporting the spin current from Pt to YIG are outstanding compared with other antiferromagnetic (AFM) metal or nonmagnetic metal (NM).
We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet$|$platinum (YIG$|$Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall like signature in Pt, sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing interface conductance $G_{mathrm{i}}$ plays a crucial role in YIG$|$Pt bilayers. In particular, our data suggest a sign change in $G_{mathrm{i}}$ between $10,mathrm{K}$ and $300,mathrm{K}$. Additionally, we report a higher order Hall effect, which appears in thin Pt films on YIG at low temperatures.
Spin Hall magnetoresistance (SMR) and magnon excitation magnetoresistance (MMR) that all generate via the spin Hall effect and inverse spin Hall effect in a nonmagnetic material are always related to each other. However, the influence of magnon excitation for SMR is often overlooked due to the negligible MMR. Here, we investigate the SMR in Pt/Y3Fe5O12 (YIG) bilayers from 5 to 300K, in which the YIG are treated after Ar+-ion milling. The SMR in the treated device is smaller than in the non-treated. According to theoretical simulation, we attribute this phenomenon to the reduction of the interfacial spin-mixing conductance at the treated Pt/YIG interface induced by the magnon suppression. Our experimental results point out that the SMR and the MMR are inter-connected, and the former could be modulated via magnon excitation. Our findings provide a new approach for separating and clarifying the underlying mechanisms.
We report the nonlocal spin Seebeck effect (nlSSE) in a lateral configuration of Pt/Y$_3$Fe$_5$O$_{12}$(YIG)/Pt systems as a function of the magnetic field $B$ (up to 10 T) at various temperatures $T$ (3 K < $T$ < 300 K). The nlSSE voltage decreases with increasing $B$ in a linear regime with respect to the input power (the applied charge-current squared $I^2$). The reduction of the nlSSE becomes substantial when the Zeeman energy exceeds thermal energy at low temperatures, which can be interpreted as freeze-out of magnons relevant for the nlSSE. Furthermore, we found the non-linear power dependence of the nlSSE with increasing $I$ at low temperatures ($T$ < 20 K), at which the $B$-induced signal reduction becomes less visible. Our experimental results suggest that in the non-linear regime high-energy magnons are over populated than those expected from the thermal energy. We also estimate the magnon spin diffusion length as functions of $B$ and $T$.
We investigate the spin Hall magnetoresistance (SMR) at room temperature in thin film heterostructures of antiferromagnetic, insulating, (0001)-oriented alpha-Fe2O3 (hematite) and Pt. We measure their longitudinal and transverse resistivities while rotating an applied magnetic field of up to 17T in three orthogonal planes. For out-of-plane magnetotransport measurements, we find indications for a multidomain antiferromagnetic configuration whenever the field is aligned along the film normal. For in-plane field rotations, we clearly observe a sinusoidal resistivity oscillation characteristic for the SMR due to a coherent rotation of the Neel vector. The maximum SMR amplitude of 0.25% is, surprisingly, twice as high as for prototypical ferrimagnetic Y3Fe5O12/Pt heterostructures. The SMR effect saturates at much smaller magnetic fields than in comparable antiferromagnets, making the alpha-Fe2O3/Pt system particularly interesting for room-temperature antiferromagnetic spintronic applications.
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