Band structure and transport properties of CrO 2

摘要: The local-spin-density approximation is used to calculate the energy bands of both ferromagnetic and paramagnetic phases metallic ${\mathrm{CrO}}_{2}$. Fermi level lies in a peak density states, phase more stable. As predicted by Schwarz, an insulating gap minority-spin between oxygen p chromium d states (``half-metallic'' behavior). resulting magnetic moment 2${\mathrm{\ensuremath{\mu}}}_{\mathrm{B}}$ per Cr atom, agreement with experiment. ${\mathrm{A}}_{1\mathrm{g}}$ Raman frequency be 587 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. Drude plasma frequencies are order 2 eV, as seen experimentally Chase. measured resistivity find electron mean free path \ensuremath{\ell}, which only few angstroms at 600 K, but, nevertheless, continues rise temperature increases. This puts ${\mathrm{CrO}}_{2}$ into category ``bad metals'' common high-${\mathrm{T}}_{\mathrm{c}}$ superconductors, high-T ${\mathrm{VO}}_{2}$, ferromagnet ${\mathrm{SrRuO}}_{3}$. In ${\mathrm{SrRuO}}_{3}$ ${\mathrm{Sr}}_{2}$${\mathrm{RuO}}_{4}$, specific-heat parameter \ensuremath{\gamma} higher than band theory predicts renormalization factor close 4.