Proposal of a general scheme to obtain room-temperature spin polarization in asymmetric antiferromagnetic semiconductors

Exploring magnetic semiconductors is one of the most important questions for spintronic applications. Although various solutions, such as dilute magnetic semiconductors, have been proposed, a practical spintronic device working at room temperature has not been realized. The key to address this issue is to find magnetic materials with both room-temperature magnetic ordering and large spin polarization around the Fermi energy level. Here, we predict a new concept of asymmetric antiferromagnetic (AFM) semiconductors (AAFMSs) with both features. The high temperature magnetic ordering originates from the AFM coupling between different transition metal ions with strong super-exchange interaction, whereas the large spin polarization around the Fermi energy level owes to d orbital mismatch among these ions. Through first-principles calculations, a family of double perovskites A₂Cr M O₆ (A =Ca ,Sr ,Ba , and M =Ru ,Os ) are predicted to be AAFMSs. This paper provides a way for developing spintronic devices working at room temperature.