Calculated electronic band structure and magnetic moments of ferrites

Controlling the electronic structure of Co1−xFe2+xOMoyer1, Vaz2, Negusse3 et al. 2011Phys. Rev. B8917740View full textAdd to dashboardCite

“…[33][34][35] The tetrahedral and octahedral sites are antiferromagnetically coupled; resulting in a magnetic moment varying between 3.65 -4.43 μ B , depending on the theoretical model. 11,12,14,15,36 Hence, magnetite is a ferrimagnet, with a large critical temperature of T c = 858 K.…”

“…Cobalt ferrite, like magnetite, is ferrimagnetic with a magnetic moment predicted by different theoretical models to be between 2.73 -3 µ B /f.u. for a perfect inverse spinel crystal structure; 11,12,15 the magnetic moment will increase with increased mixing of the Co 2+ cations between the octahedral and tetrahedral sites. Cobalt ferrite has a large magnetic anisotropy due to a spin-orbit stabilized doublet (with unquenched orbital momentum l z = ±1) ground state caused by a trigonal crystal field on the Co 2+ octahedral cations, 27, 39-45 with a cubic magnetocrystalline anisotropy constant, K 1 , which is positive and larger by over an order of magnitude than the other 3d-transition-metal spinel ferrites.…”

Orbital occupancy evolution across spin- and charge-ordering transitions in YBaFe 2 O 5

“…(1)), hence any error in point-charge estimates used in our EFG model amplifies the errors of η entered into Eqs. (3). No temperature evolution was assumed in the charge-ordered state below T V , and the set was solved for the temperature 20 K where precise crystal-structure data exist [11].…”

“…Positive populations could be obtained for both orientations allowed by β = 90°, Above T = 433 K N , the equality for the internal field disappears from the set of Eqs. (3). Considering the smooth evolution above T p towards the small positive eQV zz of the valence-mixed phase, the orbital populations can be extrapolated into the paramagnetic phase at T N .…”

“…Phase transitions from charge-ordered to valence-mixed states are behind electronic properties such as the colossal magnetoresistance in manganites [1,2] or spin-polarized conduction in magnetite [3][4][5]. The crystal structure of the charge-ordered magnetite at low temperatures has only recently been solved [6,7], and its complexity extends to the Verwey transition at 120 K [8][9][10] between the two magnetite forms.…”