The magnetic properties of MgO, ${\text{MgAl}}_2{\text{O}}_4$, ${\text{SrTiO}}_3$, ${\text{LaAlO}}_3$, LSAT, and ZnO single crystals were investigated. These crystals show three contributions to the magnetization, namely, an intrinsic diamagnetic contribution, a paramagnetic contribution, due to various transition-metal impurities, as well as a ferromagnetic contribution. The latter shows coercive field values that are rather independent of the actual crystal material. The ferromagnetic hysteresis loops of the magnetization per volume suggest a surface contribution. The origin of the ferromagnetic contribution as arising from either defect-induced ferromagnetism or ferromagnetic impurities is discussed.

• Received 2 March 2010

DOI:https://doi.org/10.1103/PhysRevB.81.214414