Nonconventional magnetism in pristine and alkali doped In_2O_3: Density functional study

摘要

Using IN_2O_3 as a host matrix, extensive calculations based on density functional theory have been carried out to understand the electronic and magnetic properties of native defects, alkali and alkaline-earth metal substitutions as disputed in recent theoretical and experimental studies. Our calculations show that the magnetism in undoped IN_2O_3 is originated from In vacancies (V_(In)) instead of O vacancies. The ferromagnetic (FM) coupling between the moments introduced by V_(In) is found strong enough to achieve room temperature ferromagnetism. Moreover, FM coupling is also strongly favored in alkali metal doping cases with negative formation energy. For all X_(In) (X_(In) = V_(In), Li_(in), Na_(in) and K_(in)) doped IN_2O_3, the induced magnetic moments are mainly localized on the first shell of O atoms around X_(in) sites. The FM coupling between the moments induced by X_(In) defects is activated by intra- and intercorrelation of the X_(In)-60_(nn) complexes. A X_(In)-O_(nn)-In_(nn)-O_(nn)-X_(In) chain is required to mediate the long-range FM coupling. However, in cases of Mg or Ca doped IN_2O_3, the ground state is nonmagnetic.