Ferromagnetism in nitrogen-doped MgO: Density-functional calculations

Mavropoulos, Ph.; Blügel, S.; Lezaic, M.

doi:10.1103/PhysRevB.80.184403

Journal Article

PreJuSER-6326

Ferromagnetism in nitrogen-doped MgO: Density-functional calculations

Mavropoulos, P.FZJ* ; Lezaic, M.FZJ* ; Blügel, S.FZJ*

2009
APS College Park, Md.

Physical review / B 80(18), 184403 (2009) [10.1103/PhysRevB.80.184403]

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Please use a persistent id in citations: http://hdl.handle.net/2128/11019 doi:10.1103/PhysRevB.80.184403

Abstract: 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 1 mu(B) 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 T-C, 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 T-C is difficult to achieve, requiring a particular attention to the choice of chemistry.

Keyword(s): J ; conduction bands (auto) ; Curie temperature (auto) ; density functional theory (auto) ; doping profiles (auto) ; exchange interactions (electron) (auto) ; ferromagnetic materials (auto) ; interstitials (auto) ; long-range order (auto) ; magnesium compounds (auto) ; magnetic moments (auto) ; magnetic relaxation (auto) ; nitrogen (auto) ; percolation (auto) ; RPA calculations (auto)