Coexistence of two different Cr ions by self-doping in half-metallic CrO2 nanorods

Abstract

We investigated the physical properties of Cr ions in half-metallic CrO2 using Cr-53 nuclear magnetic resonance (NMR). The Cr-53 NMR spectra showed two peaks with a similar intensity instead of the single peak anticipated from a uniform single valence Cr+4. Both Cr peaks exhibited a strong anisotropy in the hyperfine field and similar values in the enhancement factor and T-2 relaxation time. These results suggest the coexistence of two different Cr ions (provisionally, Cr+4 +/- 1/3) by a self-doping effect, which is a likely origin of the metallic ferromagnetism in CrO2.