LAUSR

Abstract With the first-principles calculations, the electronic structure and magnetic properties of KCaC X ( X  = O, S and Se) alloys with LiMgPdSn-type structure have been studied. The results show that KCaCO is a new bipolar ferrimagnetic semiconductor (BFS) with an integer magnetic moment of 3.00 μ B at the equilibrium lattice parameter, while KCaCS and KCaCSe are fully compensated ferrimagnetic (antiferromagnetic) semiconductors (FCFS). The strong spin polarization mainly derives from the 2 p electrons of C element in the KCaC X ( X  = O, S and Se) compounds. Under the effect of hydrostatic strain and tetragonal distortion, KCaCO alloy undergoes an interesting physics change from bipolar ferrimagnetic semiconductor (BFS) → ferrimagnetic spin-gapless semiconductor (FSGS) → general ferrimagnetic metal (GFM) transition, which indicates that the electronic and magnetic structure could be highly tuned by external temperature or pressure. A physics transition can also be found in KCaCS and KCaCSe compounds: undergoing FCFS → fully compensated ferrimagnetic semi-metal (FCFSM) → general fully compensated ferrimagnetic metal (FCFM) transitions under the hydrostatic strain and tetragonal distortion. Therefore, KCaC X ( X  = O, S and Se) compounds would be a series of potential candidates for new spintronics device.