Ultrahigh Exchange Bias Field/Coercive Field Ratio in In Situ Formed Two-Dimensional Magnetic Te-Cr₂O₃/Cr₅Te₆ Heterostructures.

Abstract

The exchange bias (EB) effect is a fundamental magnetic phenomenon, in which the exchange bias field/coercive field ratio (|H_EB/H_C|) can improve the stability of spintronic devices. Two-dimensional (2D) magnetic heterostructures have the potential to construct low-power and high-density spintronic devices, while their typically air unstable and |H_EB/H_C| lesser, limiting the possibility of applications. Here, 2D Cr₅Te₆ nanosheets have been systematically synthesized with an in situ formed ≈2 nm-thick Te doped Cr₂O₃ layer (Te-Cr₂O₃) on the upper surface by chemical vapor deposition (CVD) method. The strong and air stable EB effect, achieving a |H_EB/H_C| of up to 80% under an ultralow cooling field of 0.01 T, which is greater than that of the reported 2D magnetic heterostructures. Meanwhile, the uniformity of thickness and chemical composition of the Te-Cr₂O₃ layer can be controlled by the growth conditions which are highly correlated with the EB effect of 2D Te-Cr₂O₃/Cr₅Te₆ heterostructures. First-principles calculations show that the Te-Cr₂O₃ can provide uncompensated spins in the Cr₂O₃, thus forming strong spin pinning effect. The systematical investigation of the EB effect in 2D Te-Cr₂O₃/Cr₅Te₆ heterostructures with high |H_EB/H_C| will open up exciting opportunities in low-power and high-stability 2D spintronic devices.