Magnetic interactions in a proposed diluted magnetic semiconductor (Ba_1−xK_x)(Zn_1−yMn_y)₂P₂

By using first-principles electronic structure calculations, we have studied the magnetic interactions in a proposed BaZn₂P₂-based diluted magnetic semiconductor (DMS). For a typical compound Ba(Zn_0.944Mn_0.056)₂P₂ with only spin doping, due to the superexchange interaction between Mn atoms and the lack of itinerant carriers, the short-range antiferromagnetic coupling dominates. Partially substituting K atoms for Ba atoms, which introduces itinerant hole carriers into the p orbitals of P atoms so as to link distant Mn moments with the spin-polarized hole carriers via the p–d hybridization between P and Mn atoms, is very crucial for the appearance of ferromagnetism in the compound. Furthermore, applying hydrostatic pressure first enhances and then decreases the ferromagnetic coupling in (Ba_0.75K_0.25)(Zn_0.944Mn_0.056)₂P₂ at a turning point around 15 GPa, which results from the combined effects of the pressure-induced variations of electron delocalization and p–d hybridization. Compared with the BaZn₂As₂-based DMS, the substitution of P for As can modulate the magnetic coupling effectively. Both the results for BaZn₂P₂-based and BaZn₂As₂-based DMSs demonstrate that the robust antiferromagnetic (AFM) coupling between the nearest Mn–Mn pairs bridged by anions is harmful to improving the performance of these II–II–V based DMS materials. (paper)