Marjana Ležaić

Ferromagnetic spin coupling of 2p impurities in band insulators stabilized by an intersite Coulomb interaction: nitrogen-doped MgO.

For a nitrogen dimer in insulating MgO, a ferromagnetic coupling between spin-polarized 2p holes is revealed by calculations based on the density functional theory amended by an on-site Coulomb interaction and corroborated by the Hubbard model. It is shown that the ferromagnetic coupling is facilitated by a T-shaped orbital arrangement of the 2p holes, which is in its turn controlled by an intersite Coulomb interaction due to the directionality of the p orbitals. We thus conjecture that this interaction is an important ingredient of ferromagnetism in band insulators with 2p dopants.

Half-metallic ferromagnets for magnetic tunnel junctions by ab initio calculations

Using theoretical arguments, we show that, in order to exploit half-metallic ferromagnets in tunneling magnetoresistance TMR junctions, it is crucial to eliminate interface states at the Fermi level within the half-metallic gap; contrary to this, no such problem arises in giant magnetoresistance elements. Moreover, based on an a priori understanding of the electronic structure, we propose an antiferromagnetically coupled TMR element based on half-metallic zinc-blende chalcogenides, in which interface states are eliminated, as a paradigm of materials design from first principles. Our conclusions are supported by ab initio calculations.

First-principles prediction of high Curie temperature for ferromagnetic bcc-Co and bcc-FeCo alloys and its relevance to tunneling magnetoresistance

The authors determine from first principles the Curie temperature TC for bulk Co in the hcp, fcc, bcc, and body-centered-tetragonal (bct) phases, for FeCo alloys, and for bcc and bct Fe. For bcc Co, TC=1420K is predicted. This would be the highest Curie temperature among the Co phases, suggesting that bcc-Co∕MgO∕bcc-Co tunnel junctions offer high magnetoresistance ratios even at room temperature. The Curie temperatures are calculated by mapping ab initio results to a Heisenberg model, which is solved by a Monte Carlo method.

Ferromagnetism in nitrogen-doped MgO: Density-functional calculations

The magnetic state of nitrogen-doped MgO, with N substituting O at concentrations between 1% and the concentrated limit, is calculated with density-functional methods. The N atoms are found to be spin polarized with a moment of

A-Site and B-Site Charge Orderings in an s–d Level Controlled Perovskite Oxide PbCoO3

1{\ensuremath{\mu}}_{\text{B}}

Engineering quantum anomalous Hall phases with orbital and spin degrees of freedom

per nitrogen atom and to interact ferromagnetically via the double-exchange mechanism in the full concentration range. The long-range magnetic order is established above a finite concentration of about 1.5% when the percolation threshold is reached. The disorder is described within the coherent-potential approximation, with the exchange interactions harvested by the method of infinitesimal rotations. The Curie temperature

Structural and magnetic properties of the (001) and (111) surfaces of the half-metal NiMnSb

{T}_{\text{C}}

Exchange interactions and local-moment fluctuation corrections in ferromagnets at finite temperatures based on noncollinear density-functional calculations

, calculated within the random-phase approximation, increases linearly with the concentration, and is found to be about 30 K for 10% concentration. Besides the substitution of single nitrogen atoms, also interstitial nitrogen atoms, dimers and trimers, and their structural relaxations are discussed with respect to the magnetic state. Possible scenarios of engineering a higher Curie temperature are analyzed, with the conclusion that an increase in

HSE hybrid functional within the FLAPW method and its application to GdN

{T}_{\text{C}}

Orbital-ordering-induced ferroelectricity in SrCrO3.

is difficult to achieve, requiring a particular attention to the choice of chemistry.