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

The exchange bias (EB) effect is a fundamental magnetic phenomenon, in which the exchange bias field/coercive field ratio (|H/H|) 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/H| lesser, limiting the possibility of applications. Here, 2D CrTe nanosheets have been systematically synthesized with an in situ formed ≈2 nm-thick Te doped CrO layer (Te-CrO) on the upper surface by chemical vapor deposition (CVD) method. The strong and air stable EB effect, achieving a |H/H| 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-CrO layer can be controlled by the growth conditions which are highly correlated with the EB effect of 2D Te-CrO/CrTe heterostructures. First-principles calculations show that the Te-CrO can provide uncompensated spins in the CrO, thus forming strong spin pinning effect. The systematical investigation of the EB effect in 2D Te-CrO/CrTe heterostructures with high |H/H| will open up exciting opportunities in low-power and high-stability 2D spintronic devices.