Parasitic Magnetism in Magnetoelectric Antiferromagnet

Parasitic magnetism plays an important role in magnetoelectric spin switching of antiferromagnetic oxides, but its mechanism has not been clearly investigated. Unlike the widely obtained surface boundary magnetization in magnetoelectric Cr₂O₃ antiferromagnet, we previously reported that Al doping could produce volume-dependent parasitic magnetism (M_para) in Cr₂O₃ with the remaining magnetoelectric effect and antiferromagnetic properties. In this work, we systematically investigated the magnetic properties of M_para in Cr₂O₃ through its different exchange coupling characteristics with the ferromagnet at various conditions. The columnar grain boundaries cause an antiferromagnetic sublattice breaking to produce uncompensated spins and thus are considered to be responsible for M_para in both undoped and Al-doped Cr₂O₃. Finally, a model was proposed for the formation mechanism of the parasitic magnetism in Cr₂O₃, which explains the reported magnetic characteristics of Cr₂O₃, and some current topics such as the domain formation and motion in Cr₂O₃ during magnetoelectric spin switching. This work contributes to a deep understanding of antiferromagnetic spintronics and provides a method to realize the low-energy operation of antiferromagnetic-based magnetic random access memory.