In the previous study of longitudinal spin Seebeck effect (LSSE), the thermal gradient was often generated by inserting the sample between the cool bath and the hot bath. For practical use, this method is too cumbersome to be easily integrated into modern electrical circuits. Since the laser can be easily focused into a small region, it will be more convenient and friendly to the integrated circuit. In this paper, we systematically investigate the LSSE and spin Hall magnetoresistance (SMR) of the Pt/Y 3 Fe 5 O 12 heterostructure under focused laser-heating. We find that the extremely large voltage of inverse spin Hall effect (V ISHE ) can be obtained by reducing the diameter of laser or increasing the number of light spots. Meanwhile, even under the illumination of the ultraviolet light which will excite the electron from the valence band to the conduction band in yttrium iron garnet (YIG), the magnitude of SMR is nearly constant. It indicates that the spin transport behavior of the adjacent Pt is independent of the electron configuration of YIG. The laser-heating method to generate LSSE will be very promising for modern integrated electronic circuits and will promote the application of spin caloritronics in practice.
The electric, magnetic, and thermal properties of transition metal oxide films can be modulated by introducing polycrystalline at the macroscopic grain boundaries. Based on these points, in this work, we studied the two-channel anomalous Hall effect (AHE) in polycrystalline ferromagnetic SrRuO3 (SRO) films. The magnetic regions with different crystal directions have different coercivities, resulting in two opposite AHE channels in the polycrystalline SRO layer. However, single-crystal SRO films prepared under the same conditions are found to exhibit only one AHE. The superposition of the two AHE leads to the hump-like behavior of the Hall resistance loop, which is caused by the change of crystalline. This observation provides a new way to explain the hump-like feature of SRO.
In this work, we report the reorientation of magnetization by spin–orbit torque (SOT) in YIG/Pt bilayers. The SOT is investigated by measuring the spin Hall magnetoresistance (SMR), which is highly sensitive to the direction of magnetic moment of YIG. An external in-plane rotating magnetic field which is applied to the YIG/Pt bilayers, and the evolutions of SMR under different injected currents in the Pt layer, result in deviation of SMR curve from the standard shape. We conclude that the SOT caused by spin accumulation near the interface between YIG and Pt can effectively reorient the in-plane magnetic moment of YIG. This discovery provides an effective way to modulate YIG magnetic moments by electrical methods.
Yttrium iron garnet (YIG), as a room temperature ferrimagnetic insulator with low damping and narrow ferromagnetic resonance linewidth, has always been the research hotspot of spintronics due to its spin transport properties. Bi is one of the most common doping elements used in YIG, and some works have proved that it can tune the magnetic properties of YIG. Previous studies on Bi<sub>x</sub>Y<sub>3-x</sub>Fe<sub>5</sub>O<sub>12</sub> thin films have focused on the evolution of structure, morphology, and magnetic characteristics. Yet, the effect of Bi<sup>3+</sup>substitution of Y<sup>3+</sup> on spin transport in YIG thin films has not been systematically studied. The regulation of YIG spin transport by doping is expected to provide a new idea for the spintronics exploration of Pt/YIG system. In this work, we prepared a series of Bi<sub>x</sub>Y<sub>3-x</sub>Fe<sub>5</sub>O<sub>12</sub> films with different doping ratios by spin coating. And we investigated the effect of Bi<sup>3+</sup> on morphology, structure and spin transport properties of YIG films. The results show that Bi doping does not change the crystal structure of YIG. Absorption of the films increases and the bandgap decreases with the increase of doping ratio. XPS indicates the co-existence of Bi<sup>3+</sup> and Bi<sup>2+</sup>. The regulation of Bi doping on spin transport is reflected in the fact that the magnon diffusion length of Bi<sub>x</sub>Y<sub>3-x</sub>Fe<sub>5</sub>O<sub>12</sub> films is significantly smaller than that of pure YIG films. Meanwhile, we found that the obvious spin Hall magnetoresistance can still be detected in the Pt/Bi<sub>x</sub>Y<sub>3-x</sub>Fe<sub>5</sub>O<sub>12</sub> heterostructure, and the amplitude is the largest when x=0.3.
The oxide two-dimensional electron gases (2DEGs) have been intensively studied for both fundamental and applied research over the past decade. It is known that the electrostatic and optical gating can both effectively modulate the transport behavior of 2DEG. However, the in-plane carrier distribution under the light assisted electrostatic gating is scarcely studied. In this study, we systematically investigate this problem in the 3d and 5d oxide-based 2DEGs samples, and observe strong lateral photovoltaic effect (LPE) in both of the 2DEGs. Remarkably, the lateral voltage is strongly dependent on the gating electrical field especially in the 5d oxide-based 2DEGs and its signs are absolutely reversed as the bias voltage becomes negative. Through systematic research, it is found that the leak current caused by light assisted electrostatic gating, strongly affects the in-plane carrier distribution. These results have significance for fundamental research and device application based on the photovoltaic effect of oxide 2DEGs.
Novel transport behavior of carriers always generates new types of electronic elements. For traditional resistor element, the voltage is directly proportional to drift current regardless of Joule heat, which can be credibly described by Ohm’s law. There are still some new types of materials such as memristor and Weyl metal that do not follow Ohm’s law, and they have drawn significant attention. In this work, we theoretically and experimentally investigated the transport behavior of diffusion current near the interface of the silicon-based Schottky junction. It is clearly observed that the output voltage in the diffusion path could be higher (lower) when the resistance was lower (higher), even under identical diffused current. Deep theoretical analysis is also carried out, which is found to be in good agreement with the experimental results. These results suggest that the transport behavior of diffusion carriers is quite different from the drift carriers. This study may provide a foundation for fundamental research and device application based on the transport of diffusion carriers near the interface.
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