Band structure and transport properties ofCrO2

Abstract

Local Spin Density Approximation (LSDA) is used to calculate the energy bands of both the ferromagnetic and paramagnetic phases of metallic CrO2. The Fermi level lies in a peak in the paramagnetic density of states, and the ferromagnetic phase is more stable. As first predicted by Schwarz, the magnetic moment is 2 µB per Cr atom, with the Fermi level for minority spins lying in an insulating gap between oxygen p and chromium d states ("half-metallic" behavior.) The A1g Raman frequency is predicted to be 587 cm −1 . Drude plasma frequencies are of order 2eV, as seen experimentally by Chase. The measured resistivity is used to find the electron mean-free path ℓ which is only a few angstroms at 600K, but nevertheless, resistivity continues to rise as temperature increases. This puts CrO2 into the category of "bad metals" in common with the high Tc superconductors, the high T metallic phase of VO2, and the ferromagnet SrRuO3. In common with both SrRuO3 and Sr2RuO4, the measured specific heat γ is higher than band theory by a renormalization factor close to 4.

Magnetic anisotropy of textured CrO 2 thin films investigated by X-ray magnetic circular dichroism

“…First, 1 eV above threshold, which is unambiguously identified as unoccupied t 2g majority states and, second, a broader feature around 3 eV above, which corresponds to a mixture of t 2g e g minority and the e g majority states [27]. The latter represents band-structure-related values [1][2][3]26]. This energy separation is also present in CrO 2 L 2,3 spectra, which have a more complicated shape compared to simple pure and metallic TM spectra.…”

“…Influences of the core hole could be considered by a configurationinteraction scheme [24]. Due to this projection behavior, the main features could be understood by quantitative comparison to recent band-structure calculations [1][2][3]26]. O K spectra and band-structure calculations could give similar information.…”

“…The theoretically predicted 100% spin polarization at the Fermi energy, ε F , of CrO 2 makes it a promising material for magnetoelectronic devices [1][2][3]. According to Jullière's model, the magnetoresistance (MR) of a ferromagnet/insulator/ferromagnet tunnel junction depends on the spin polarization of the electrode material used [4].…”

Calculated electronic structure and x-ray magnetic circular dichroism of CrO2

“…The electronic structure of CrO 2 has been extensively reported in the literature 16,17,18,19,20,21,22,23,25 so in this section we briefly discuss the density of states and compare with the ealier works. Figure 1 shows the density of states (spin up and down) of Cr-3d and O-2p states.…”

“…These compounds serve as perspective materials in the field of spintronics 15 . Numerous theoretical works are available for CrO 2 explaining the electronic structure, bonding, optical and magneto-optical properties and magneto-crystalline anisotropy(MCA) etc 16,17,18,19,20,21,22,23,24,25 . Because of the uniaxial crystal structure, CrO 2 is expected to have a large magnetic anisotropy which makes it the favoured material for magneto-optical recording.…”