Parasitic Magnetism in Magnetoelectric Antiferromagnet

摘要

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 (Mpara) in Cr2O3 with the remaining magnetoelectric effect and antiferromagnetic properties. In this work, we systematically investigated the magnetic properties of Mpara 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 Mpara 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.