Anisotropy of the magnetization of a dilute magnetic oxide

High-quality (1 1 0) films of ZnO, undoped or doped with the 3d transition metals from Sc to Cu, have been prepared on R-cut sapphire. Most of the films, including the one doped with Sc, exhibit ferromagnetic moments at room temperature greater than 100 μ(B) nm(-2), which are remarkably anisotropic. The moment in 1 T is usually larger, by a factor of up to three, when the field is applied perpendicular to the plane of the film than it is in a parallel direction. Strong in-plane anisotropy is observed for Co. The data suggest a new type of ferromagnetism related to defects at the film-substrate interface. © 2004 Elsevier B.V. All rights reserved.