Shubnikov–de Haas oscillations in half-metallic ferromagnetic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">CrO</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> epitaxial films

We present a study of the low-temperature, high-field magnetotransport behavior of epitaxially grown <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>CrO</a:mi><a:mn>2</a:mn></a:msub></a:math> thin films on (100) <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:msub><b:mi>TiO</b:mi><b:mn>2</b:mn></b:msub></b:math> 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 <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:msup><c:mi>T</c:mi><c:mrow><c:mn>4.5</c:mn></c:mrow></c:msup></c:math> 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 <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mn>1</d:mn><d:mo>/</d:mo><d:mo form="prefix">cos</d:mo><d:mi>θ</d:mi></d:mrow></d:math> 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 <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:msub><f:mi>CrO</f:mi><f:mn>2</f:mn></f:msub></f:math> 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.