The core of spintronics devices such as magnetic storage and magnetic logic is the transfer of spin information. In particular, the generation, manipulation, and detection of spin information is a fundamental problem in spintronics. Spinning information in existing spintronics relies mainly on conduction electrons in metals. An interesting question is whether other particles or even quasiparticles can be used as carriers for spin information. As a quasi-particle of the low-energy excited state in ferromagnetic magnets, a magnetite is a boson, and a quantized magneton carries a Planck constant spin angular momentum. In metals, the transport of conductive electron spins is usually accompanied by the transport of charges. In the ferromagnetic insulator, there is only the transport of spin information transmitted by the magnetron without charge transport, so that the power consumption of the device can be significantly reduced. In 2012, the team of Professor Zhang Yufeng from the University of Arizona in the United States theoretically predicted the magnetic current-assisted current drag phenomenon in the heavy metal/ferromagnetic insulator/heavy metal (HM/MI/HM) sandwich structure [SS-L. Zhang and S. Zhang, Phys. Rev. Lett. 109 (2012) 096603; Phys. Rev. B 86 (2012) 214424]. The current in one side of the heavy metal generates spin accumulation at the HM/MI interface due to the spin Hall effect, and the MI can be excited by the exchange interaction between the conduction electrons in the HM and the sd electrons in the local magnetic moment in the MI. The magnetons in the magnet, the magnetons diffuse in the MI to form magnetic substreams, and the HMs in the magnetron stream to the other side convert to spin currents that pass through the anti-spin Hall effect so that they can be on the other side. The HM generates current. The research team led by Han Xiufeng, a researcher at the Institute of Physics, Chinese Academy of Sciences/Beijing National Laboratory for Condensed Matter Physics, uses magnetron sputtering technology combined with high temperature heat treatment process to prepare and optimize a series of samples to overcome In the past, the limitation that YIG can only be fabricated on a single-crystal GGG substrate, a novel heavy metal/ferromagnetic insulator/heavy metal layered spin valve structure of Pt/YIG/Pt was designed and fabricated on a Si-SiO2 substrate. The transmission electron microscope (TEM) and high angle circular dark field image (HAADF) show that YIG has a good crystal structure, and the interface between Pt and YIG is clear. The vibrating sample magnetometer (VSM) and ferromagnetic resonance absorption spectrum (FMR) show that the sample has strong magnetic properties and low damping coefficient at room temperature. The bottom and top Pt are used as the injection end and the detection end respectively, the injection end current is applied in the x direction, and the detection end voltage is also measured in the x direction. This experiment overcomes the shortcomings of previous in-plane non-local spin valves that can only detect magnetron accumulation in YIG, and cannot directly detect magnetic substreams in YIG, and can directly compare experimental results with theoretical predictions. The research group conducted a comparative analysis of the experimental and theoretical models by teaming with Zhang Haofeng team and found that the current drag coefficient obtained at the room temperature can reach the order of 10-4, and the linear relationship between the detection terminal voltage and the injection terminal current is achieved. No off-current was observed, and the detection terminal voltage and the YIG magnetization were proportional to the square of the component in the y direction. This characteristic was in contrast to the previous spin transfer torque effect of YIG ferromagnetic resonance [Y. Kajiwara et al., Nature 464 (2010) 262] and the temperature gradient caused by the spin Seebeck effect [K. Uchida et al., Nat. Mater. 9 (2010) 894]. At the YIG and Pt interfaces, the conversion efficiency of spins and magnetons is proportional to the number of equilibrium state magnetons in YIG. For the ideal interface and quadratic distribution of the magnetic spectrum, the detection terminal voltage and temperature are 5/2 times. Square is proportional. By fitting the dependence of the probe voltage on the thickness of the YIG, the decay length of the flux in the YIG can be 38 nm. This is similar to the results reported by other groups on the spin Seebeck effect in YIG [SM Rezende] Et al., Phys. Rev. B 89 (2014) 014416]. The new layered spin valve structure Pt/YIG/Pt—heavy metal/ferromagnetic insulator/heavy metal prepared by this research work has important experimental and theoretical guiding significance for studying the transport properties of magnetons in ferromagnetic insulators. , is a very representative breakthrough in the "spintronics of ferromagnetic insulators", it fully shows that a new class of spintronics core devices using ferromagnetic insulators as the spin information carrier has important applications The prospect, that is, the use of a magnetron in a ferromagnetic insulator as a carrier for spin information, can overcome the influence of Joule heat generated by charge flow and have low energy consumption characteristics; and this layer of the vertical direction prepared on Si-SiO2 The spin valve structure can be matched with the existing large-scale integrated circuit process, and it can contribute to the integration and comprehensive utilization of non-rotating electronic devices and semiconductor microelectronic devices. Research progress on this work has been published in Phys. Rev. B 93 (2016) 060403(R). Related research has been supported by the National Natural Science Foundation of China, the Ministry of Science and Technology, and the Chinese Academy of Sciences related project funds.
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All-electrical methods for the study of magnetic transport properties in ferromagnetic insulators have progressed