Strain-induced magnetic anisotropies in epitaxial CrO2 thin films probed by FMR technique

Abstract

Epitaxial CrO2 thin films were grown onto TiO2 (1 0 0) single-crystalline substrates by chemical vapour deposition (CVD) process with use of the solid precursor CrO3. The CrO2 films with thickness of 27 and 65 nm were deposited onto TiO2 substrates pre-etched in the diluted HF. The magnetic properties of the epitaxial chromium-dioxide films have been probed by the ferromagnetic resonance (FMR) technique. Analysis of the FMR spectra shows that the magnetic behaviour of the CrO2 films results from a competition between magnetocrystalline and strain anisotropies. The thin films are heavily strained due to lattice mismatch of CrO2 epitaxial film with the TiO2 single-crystalline substrate. For the thinnest film (27 nm) the stress anisotropy dominates, and the magnetic easy axis switches from the c direction to the b direction of the rutile structure. Unusual angular dependence of the resonance signal and multiple FMR modes are observed for the film with the thickness of 65 nm, where a partial strain relaxation results in appearance of two magnetic phases with mutually perpendicular easy axes along the c and b directions. © 2005 Elsevier B.V. All rights reserved.