FMR study of strain-induced magnetic anisotropies in CrO_2 thin films

摘要

Epitaxial CrO_2 thin films were grown on TiO_2 (100) single-crystalline substrates by chemical vapour deposition (CVD) process with use of CrO_3 solid precursor. The films with different thickness (27-530 nm) were studied by Ferromagnetic Resonance (FMR) technique. Strong dependence of FMR signal on the film thickness was observed in the series of CrO_2 films deposited onto the pre-etched TiO_2 substrates. It is shown that the magnetic behaviour of the CrO_2 films arises from competition between magnetocrystalline and strain anisotropies that favour the [001] and [010] magnetization directions, respectively. For the thinnest film the strain anisotropy dominates, and the magnetic easy axis switches from [001] to the [010] direction. On the contrary, the CrO_2 film grown on the unetched substrate demonstrates essentially strain-free magnetic anisotropy behaviour.