Magnetic and electronic properties of nitrogen-doped lanthanum sesquioxide La2O3 as predicted from first principles

Using the ab initio FLAPW-GGA method we examine the electronic and magnetic properties of nitrogen-doped non-magnetic sesquioxide La2O3 emphasizing the role of doping sites in the occurrence of d0-magnetism. We predict the magnetization of La2O3 induced by nitrogen impurity in both octahedral and tetrahedral sites of the oxygen sublattice. The most interesting results are that (i) the total magnetic moments (about 1 {\mu}B per supercells) are independent of the doping site, whereas (ii) the electronic spectra of these systems differ drastically: La2O3:N with six-fold coordinated nitrogen behaves as a narrow-band-gap magnetic semiconductor, whereas with four-fold coordinated nitrogen is predicted to be a magnetic half-metal. This effect is explained taking into account the differences in N-2pz versus N-2px,y orbital splitting for various doping sites. Thus, the type of the doping site is one of the essential factors for designing of new d0-magnetic materials with promising properties.