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 $A_2\mathrm{Cr}M{\mathrm{O}}_6$ ($A=\mathrm{Ca},\mathrm{Sr},\mathrm{Ba}$, and $M=\mathrm{Ru},\mathrm{Os}$) are predicted to be AAFMSs. This paper provides a way for developing spintronic devices working at room temperature.

• Received 26 December 2014
• Revised 2 July 2015

DOI:https://doi.org/10.1103/PhysRevB.92.125202