Evidence for two-band magnetotransport in half-metallic chromium dioxide

By S. Watts, S. Wirth, S. V. Molnár, A. Barry, J. Coey. 2000

186 citations recorded by the source corpus.

Magnetotransport measurements were made on patterned, (110) oriented ${\mathrm{CrO}}_{2}$ thin films grown by the high-pressure, thermal decomposition of ${\mathrm{CrO}}_{3}$ onto rutile substrates. The low-temperature Hall effect exhibits a sign reversal from positive to negative as the magnetic field is increased above 1 T, which may be interpreted within a simple two-band model as indicating the presence of highly mobile $({\ensuremath{\mu}}_{h}=0.25{\mathrm{m}}^{2}/\mathrm{V}\mathrm{}\mathrm{s})$ holes as well as a much larger number of less mobile electrons $(n=0.4$ electrons/Cr). Between 50 and 100 K, the field at which the sign reversal occurs rapidly increases and a contribution from the anomalous Hall effect becomes significant, while the large, positive transverse magnetoresistance (MR) observed at low temperatures changes over to a predominantly negative MR. These changes correlate with a thermally activated dependence in the resistivity of the form ${T}^{2}{e}^{\ensuremath{-}\ensuremath{\Delta}/T}$ with $\ensuremath{\Delta}\ensuremath{\approx}80\mathrm{K},$ reflecting the lack of temperature dependence in the resistivity at low temperatures and a ${T}^{2}$ behavior above 100 K. The high mobilities at low temperature which result in the observed positive MR reflect the suppression of spin-flip scattering expected for a half-metallic system. However, the changes in magnetotransport above the temperature $\ensuremath{\Delta}$ must be due to the onset of spin-flip scattering, even though ${k}_{B}\ensuremath{\Delta}$ is much less than the expected energy gap in the minority spin density of states. The significance of $\ensuremath{\Delta}$ is discussed in terms of recent models for another half-metallic system, the perovskite manganites, and the possible formation of ``shadow bands.''

Subfields: Electronic, Optical and Magnetic Materials, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/7a02335456e99f9532ea7b71e719761d0f06a6b7

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In Electronic, Optical and Magnetic Materials

In Materials Chemistry

Citations in the corpus

Oxide Spintronics (2007, background): “The low-temperature resistivity is of the order of 1 μΩ · cm in high-quality thin films [119].”
Half-metallic ferromagnets: From band structure to many-body effects (2007, result): “The transport properties of CrO2 were investigated in detail (Watts et al., 2000) and interpreted in terms of a two-band model, very much in line with the double exchange model for CrO2.”