<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Mavropoulos, Phivos</style></author><author><style face="normal" font="default" size="100%">Lezaic, Marjana</style></author><author><style face="normal" font="default" size="100%">Blügel, Stefan</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Ferromagnetism in nitrogen-doped MgO: Density-functional calculations</style></title><secondary-title><style face="normal" font="default" size="100%">PHYSICAL REVIEW B</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2009</style></year><pub-dates><date><style  face="normal" font="default" size="100%">NOV</style></date></pub-dates></dates><number><style face="normal" font="default" size="100%">18</style></number><volume><style face="normal" font="default" size="100%">80</style></volume><pages><style face="normal" font="default" size="100%">184403</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">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.</style></abstract></record></records></xml>