MAGNETIC PROPERTIES OF CrO_2 THIN FILMS STUDIED BY FMR TECHNIQUE

摘要

Epitaxial CrO_2 thin films on TiO_2 (100) single-crystal substrates were fabricated by CVD process with use of solid (CrO_3) and liquid (CrO_2Cl_2) precursors. Magnetic properties of the films were studied by ferromagnetic resonance technique. Strong dependence of magnetic anisotropies on the thickness of CrO_2 films was observed in the series prepared using the CrO_3 solid precursor. It was found that it is due to magnetoelastic anisotropy in the plane of the CrO_2 film caused by lattice mismatch with the TiO_2 substrate. On the contrary, the anisotropy parameters of CrO_2Cl_2-based films demonstrate very weak variations with the thickness. Atomic force microscopy studies showed that the different behaviour apparently relates to various morphologies of the films prepared with solid and liquid precursors. In the CrO_2Cl_2 liquid- precursor series the individual CrO_2 grains, growing epitaxially on the TiO_2 substrate, form fairly regular rectangular-shaped blocks with the lateral size of about 150 nm. Breaks in the nearest to the substrate layer of the epitaxial CrO_2 film result in quick relaxation of the tensile stress, arising due to the lattice mismatch, and decrease greatly the effect of magnetoelastic anisotropy in the CrO_2Cl_2 liquid-precursor films.