Large and Tunable Magnetoresistance in Cr1−xTe/Al2O3/Cr1−xTe Vertical Spin Valve Device

Abstract The recent discovery of 2D ferromagnetic materials provides new opportunities for fabricating 2D ferromagnets‐based spin valve devices and exploring related novel physics. However, up to now, almost all works adopt a spin valve configuration by inserting different types of 2D materials into the gap between two 2D ferromagnetic electrodes as barrier spacer, rather than applying traditional tunneling barrier, such as Al 2 O 3 films grown by atomic layer deposition (ALD), probably attributed to the instability and incompatibility for the widely explored 2D ferromagnets (CrI 3 , Fe 3 GeTe 2 ) to the ALD growth process. Here, Cr 1− x Te, an air‐stable 2D ferromagnetic metal grown by chemical vapor deposition, show excellent compatibility to ALD process of depositing Al 2 O 3 films. The nonencapsulated Cr 1− x Te/Al 2 O 3 /Cr 1− x Te vertical spin valve devices demonstrate high magnetoresistance ratio of ≈28% and large spin polarization of 0.36 at 2 K. Furthermore, a gradual evolution from tunneling to metallic spin‐valve behavior is found upon decreasing Al 2 O 3 spacer thickness. The work is constructive and illuminating for connecting the 2D ferromagnetic electrodes with traditional tunneling spacers for fundamental research and device applications.