Interfacial charge transfer induced antiferromagnetic metals and magnetic phase transition in (CrO2) m /(TaO2) n superlattices

Abstract

As a class of remarkable spintronic materials, intrinsic antiferromagnetic (AFM) metals are rare. The exploration and investigation of AFM metals are still in its infancy. Based on first-principles calculations, the interface-induced magnetic phenomena in the (CrO2) m /(TaO2) n superlattices are investigated, and a new series of AFM metals is predicted. Under different ratios of with varying valence states of Cr, the (CrO2) m /(TaO2) n superlattices exhibit three different phases, including the AFM metal, the AFM semiconductor, and the ferromagnetic (FM) metal. In the AFM semiconducting phases, the intra-CrO2-monolayer magnetic exchange interaction is systematically discussed, corresponding to m = 1 or m = 2. Both the localization of the Cr 3 d orbitals and the crystal-field splitting are crucial for magnetic ordering in super-exchange interactions. Based on the analyses of the AFM semiconducting phases with m = 1 and m = 2, the mechanisms of AFM metallic phases with radios of and are discussed in detail. Additionally, the AFM metallic superlattices can be tuned into a FM metallic phase by applying strain in the c-direction, such as a compression of 7% in the (CrO2)1/(TaO2)3 superlattice, and a tensile strain of 7% in the (CrO2)2/(TaO2)3 superlattice. The phase diagram of the (CrO2) m /(TaO2) n superlattices is obtained as a function of the layer thickness. This work provides new insights about realizing and manipulating AFM metals in artificial superlattices or heterostructures in experiments.