1State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China 2Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China 3Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing 100875, China
Abstract：The emergent van der Waals magnetic material is a promising component for spintronic devices with novel functionalities. Here, we report a transition of negative-to-positive magnetoresistance in Fe$_{3}$GeTe$_{2}$/Cr$_{2}$Ge$_{2}$Te$_{6}$/ Fe$_{3}$GeTe$_{2}$ van der Waals all-magnetic tunnel junctions with increasing the applied bias voltage. A negative magnetoresistance is observed first in Fe$_{3}$GeTe$_{2}$/Cr$_{2}$Ge$_{2}$Te$_{6}$/Fe$_{3}$GeTe$_{2}$ tunnel junctions, where the resistance with antiparallel aligned magnetization of two Fe$_{3}$GeTe$_{2}$ electrodes is lower than that with parallel alignment, which is due to the opposite spin polarizations of two Fe$_{3}$GeTe$_{2}$ electrodes. With the bias voltage increasing, the spin polarization of the biased Fe$_{3}$GeTe$_{2}$ electrode is changed so that the spin orientations of two Fe$_{3}$GeTe$_{2}$ electrodes are the same. Our experimental observations are supported by the calculated spin-dependent density of states for Fe$_{3}$GeTe$_{2}$ electrodes under a finite bias. The significantly bias voltage-dependent spin transport properties in van der Waals magnetic tunnel junctions open a promising route for designing electrical controllable spintronic devices based on van der Waals magnets.
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2023, Vol. 40 
