Temperature-dependent orbital-moment anisotropy in dilute magnetic oxides

Authors

Jun Zhang, University of Nebraska - LincolnFollow
Ralph Skomski, University of Nebraska-LincolnFollow
Yongfeng Lu, University of Nebraska - LincolnFollow
David J. Sellmyer, University of Nebraska-LincolnFollow

Date of this Version

June 2007

Comments

Published in PHYSICAL REVIEW B 75, 214417 2007. ©2007 The American Physical Society. Used by permission.

Abstract

A striking magnetization anisotropy in thin films of vanadium-doped stannic oxide is reported and investigated. The single-crystalline Sn_1-xV_xO₂ (0≤x≤0.1) thin films, grown on Al₂O₃ substrate, are (101) oriented and exhibit a temperature-dependent in-plane anisotropy of the saturation magnetization. The in-plane magnetic moment reaches a maximum close to the [101¯] direction, but the anisotropy axis is incompatible with the crystalline structure of the SnO₂ thin films. However, it is consistent with V atoms occupying uniaxially distorted octahedral interstices, thus breaking the symmetry of the film. The moment anisotropy decreases gradually with increasing temperature and persists to temperatures above room temperature. It is modeled as a spin-orbit effect involving the hopping of orbital-current loops, as contrasted to isotropic Heisenberg exchange, and the temperature dependence of the magnetism is explained on the basis of a thermal admixture of nearly degenerate crystal-field states. The phenomena may be relevant to a wide range of dilute magnetic oxides.