Magnetism and Electronic Structure in ZnFe$_2$O$_4$ and MnFe$_2$O$_4$

We calculate the structural, electronic, and magnetic properties of MnO from first principles, using the full-potential linearized augmented planewave method, with both local-density and generalized-gradient approximations to exchange and correlation. We find the ground state to be of rhombohedrally distorted B1 structure with compression along the [111] direction, antiferromagnetic with type-II ordering, and insulating, consistent with experiment. We show that the distortion...

In view of recent controversy regarding the orbital order in the frustrated spinel ZnV2O4, we analyze the orbital and magnetic groundstate of this system within an ab initio density functional theory approach. While LDA+U calculations in the presence of a cooperative Jahn-Teller distortion stabilize an A-type staggered orbital order, the consideration of relativistic spin-orbit effects unquenches the orbital moment and leads to a uniform orbital order with a net magnetic mome...

We have employed first-principles electronic structure calculations to examine the hypothetical (but plausible) oxide spinel, LiCr2O4 with the d^{2.5} electronic configuration. The cell (cubic) and internal (oxygen position) structural parameters have been obtained for this compound through structural relaxation in the first-principles framework. Within the one-electron band picture, we find that LiCr2O4 is magnetic, and a candidate half-metal. The electronic structure is sub...

In this paper we show that spinel ferrite nanocrystals (NiFe2O4, and CoFe2O4) can be texturally embedded inside a ZnO matrix by ion implantation and post-annealing. The two kinds of ferrites show different magnetic properties, e.g. coercivity and magnetization. Anomalous Hall effect and positive magnetoresistance have been observed. Our study suggests a ferrimagnet/semiconductor hybrid system for potential applications in magneto-electronics. This hybrid system can be tuned b...

The electronic structures of Fe-doped III-V semiconductors were studied by first-principles supercell calculation. It was found that their electronic structures are basically the same as those of Mn-doped ones except that the extra electron of Fe compared to Mn occupies either majority-spin $p$-$d$ hybridized antibonding states ($t_{a,\uparrow}$) or minority-spin $e$ states ($e_{\downarrow}$) and that the center of gravity of the $d$ partial density of states is higher for Fe...

Experimentally, the intermetallic compound Mn$_{4}$FeGe$_{3}$ has been recently shown to exhibit enhanced magnetic properties and spin polarization compared to the Mn$_{5}$Ge$_{3}$ parent compound. The present {\em ab-initio} study focusses on the effect of Fe substitution on the electronic and magnetic properties of the compound. Our calculations reveal that the changes on the Fermi surface of the doped compound are remarkable and provide explanations for the enhanced spin-p...

LaCu3Fe4O12 undergoes a phase transition at 393 K involving the spin order (SO) of the Fe sites and the charge order (CO) resulting in Cu-Fe intersite charge transfer. On the basis of density functional calculations, we show that this simultaneous CO/SO phenomenon is a consequence of two electronic effects, namely, the competition between the Fe-Fe and Fe-Cu antiferromagnetic spin exchange and the dependence of the width of the Fe d-block bands on the SO of the Fe atoms.

The electronic structures of the cubic and tetragonal $\mathrm{MnV}_2\mathrm{O}_4$ have been studied by using hybrid-exchange density functional theory. The computed electronic structure of the tetragonal phase shows an anti-ferro orbital ordering on V sites and a ferrimagnetic ground state (the spins on V and Mn are anti-aligned). These results are in a good agreement with the previous theoretical result obtained from the local-density approximation+$U$ methods [S. Sarkar, e...

The magnetic properties of Mn, Co and Ni substituted Fe4N are calculated from first principles theory. It is found that the generalized gradient approximation reproduces with good accuracy the magnetic moment and equilibrium volume for the parent Fe4N structure, with the atomic moment largest for the Fe atom furthest away from the N atom (Fe I site), approaching a value of 3 muB/atom, whereas the Fe atom closer to the N atom (Fe II site) has a moment closer to that of bcc Fe....

This a review article, which presents a general framework for the analysis of interatomic magnetic interactions in the spin-density-functional theory, which is based on the magnetic force theorem, make a link with the models for transition-metal oxides, and gives several examples of how this strategy can be used for the analysis of magnetic properties of colossal-magnetoresistive perovskite manganites, double perovskite and pyrochlore compounds.