Abstract
By using the density functional theory within Perdew-Burke-Ernzerh of generalized gradient approximation, the electronic structures and magnetic properties of Ba 1 − x K x ( Cd 1 − y Mn y ) 2 As 2 system were investigated. Undoped compound BaCd 2 As 2 is a semiconductor crystallized with a hexagonal CaAl 2 Si 2 −type structure. After local moments doping via isovalent (Cd2+, Mn2+) substitutions, Ba ( Cd 1 − y Mn y ) 2 As 2 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 1 − x K x ( Cd 1 − y Mn y ) 2 As 2 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 4 p and Mn 3 d orbitals. Moreover, hypothetical supercells Ba 10 K 2 Cd 22 Mn 2 As 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 1 − x K x ( Cd 1 − y Mn y ) 2 As 2 system with small lattice has more holes amount and better holes mobility, leading to a higher Curie temperature for the CaAl 2 Si 2 -type structure DMSs.