Shubnikov–de Haas oscillations in half-metallic ferromagnetic CrO 2 epitaxial films

We present a study of the low-temperature, high-field magnetotransport behavior of epitaxially grown {CrO}₂ thin films on (100) {TiO}₂ substrates. Electron transport measurements confirm high sample quality, with a residual resistivity ratio as large as 45. A logarithmic fit of the low-temperature regime yields a {T}^4.5 power law, indicative of the elusive double-magnon scattering in half-metallic ferromagnets. Angle-dependent anisotropic magnetoresistance (AMR) measurements reveal a large projected density of states along [001] with a maximum AMR value of 2.4%. Pronounced, axis-dependent Shubnikov–de Haas (SdH) oscillations are observed in the longitudinal magnetoresistance (MR), with discrete Landau levels mapped at various tilt angles of the magnetic field. Their angular dependence follows a 1/cosθ relation pointing to a highly anisotropic Fermi surface, and amplitude scaling adheres closely to the thermodynamic Lifshitz-Kosevich formalism. The out-of-plane MR reaches 6.58%, the largest reported for {CrO}₂ thin films. Notably, this study presents an observation of SdH oscillations in a half-metallic oxide with near-perfect spin polarization, a significant advancement in the field of spintronics.