A neutron diffraction study of half-metallic ferromagnet CrO2 nanorods

Temperature dependent micro-structural and magnetic properties of CrO2 nanorods have been studied by neutron diffraction from 3.5 K to 450 K. Rietveld analysis considering the anisotropic shape of nanorods suggested that each CrO2 nanorod probably consisted of a few microscopically oriented grains. Around the ferromagnetic transition temperature (∼395K), a dominant lattice distortion in the tetragonal phase was not a change along the cc axis, but a contraction along the ab axes perpendicular to the lengthwise direction of the nanorods, which was caused by an apical bond contraction in CrO6 octahedra. The obtained structural and magnetic data of CrO2 nanorods were compared with the temperature dependent resistivity of the epitaxial CrO2/TiO2 film, and strong couplings between structural, magnetic, and electric properties in the half-metallic ferromagnet CrO2 were observed.