title: Magnetism without magnetic ions: percolation, exchange, and formation energies of magnetism-promoting intrinsic defects in CaO.
abstract: We investigate theoretically the prospects of ferromagnetism being induced by cation vacancies in nonmagnetic oxides. A single Ca vacancy V(0)(Ca) has a magnetic moment due to its open-shell structure but the ferromagnetic interaction between two vacancies extends only to four neighbors or less. To achieve magnetic percolation on a fcc lattice with such an interaction range one needs a minimum of 4.9% vacancies, or a concentration 1.8 x 10(21) cm(-3). Total-energy calculations for CaO show, however, that due to the high vacancy formation energy even under the most favorable growth conditions one can not obtain more than 0.003% or 10(18) cm(-3) vacancies at equilibrium, showing that a nonequilibrium vacancy-enhancement factor of 10(3) is needed to achieve magnetism in such systems.
authors.affiliation: National Renewable Energy Laboratory, Golden, Colorado 80401, USA.
authors.forename: J
authors.initials: J
authors.lastname: Osorio-Guillén
authors.forename: S
authors.initials: S
authors.lastname: Lany
authors.forename: S V
authors.initials: SV
authors.lastname: Barabash
authors.forename: A
authors.initials: A
authors.lastname: Zunger