Electronic structures and magnetic properties of a II-II-V based diluted magnetic semiconductor Ba1−xKx(Cd1−yMny)2As2 with decoupled charge and spin doping
By using the density functional theory within Perdew-Burke-Ernzerh of generalized gradient approximation, the electronic structures and magnetic properties of Ba K Cd Mn As 1 1 22 - - xx y y ( ) system were investigated. Undoped compound BaCd As 2 2 is a semiconductor crystallized with a hexagonal CaAl Si 2 2−typestructure. After local moments doping via isovalent(Cd2+, Mn2+) substitutions, Ba Cd Mn As ( ) 1 22 -y y is antiferromagnetic system, which is attributed to the superexchange interactions between the Mn2+ ions in the high spin state. With itinerant holes introduced via off-stoichiometry (Ba2+, +K )substitutions, Ba K Cd Mn As 1 1 22 - - xx y y ( ) system (except for the system doped with the most nearest neighbor Mn-Mn pair) changes from antiferromagnetic to ferromagnetic, resulted from the indirect exchange interactions based on p − d exchange coupling between As 4p and Mn 3d orbitals. Moreover, hypothetical supercells Ba K Cd Mn As 10 2 22 2 24 with different lattice parameters under mechanical compression and expansion were calculated to study the effect of itinerant holes on the Curie temperature. Our results reveal that the Ba K Cd Mn As 1 1 22 - - xx y y ( ) system with small lattice has more holes amount and better holes mobility, leading to a higher Curie temperature for the CaAl Si 2 2-type structure DMSs.