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

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)_nsuperlattices are investigated, and a new series of AFM metals is predicted. Under different ratios ofm:nwith varying valence states of Cr, the (CrO₂)_m/(TaO₂)_nsuperlattices exhibit three different phases, including the AFM metal, the AFM semiconductor, and the ferromagnetic (FM) metal. In the AFM semiconducting phases, theintra-CrO₂-monolayer magnetic exchange interaction is systematically discussed, corresponding tom = 1 orm = 2. Both the localization of the Cr 3 dorbitals and the crystal-field splitting are crucial for magnetic ordering in super-exchange interactions. Based on the analyses of the AFM semiconducting phases withm = 1 andm = 2, the mechanisms of AFM metallic phases with radios ofm:n<1/2and1/2c-direction, such as a compression of 7% in the (CrO₂)₁/(TaO₂)₃superlattice, and a tensile strain of 7% in the (CrO₂)₂/(TaO₂)₃superlattice. The phase diagram of the (CrO₂)_m/(TaO₂)_nsuperlattices 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.