Investigation of electronic structure, magnetic stability, spin coupling, and thermodynamic properties of novel antiferromagnets XMn2Y2 (X = Ca, Sr; Y = P, As)

Abstract

In the present work, the structural, electronic, magnetic, and thermodynamic properties of ternary compounds of composition XMn2Y2 (X = Ca, Sr; Y = P, As) are reported. The calculations are performed using the full potential augmented plane wave method (FP-APW) within the framework of density functional theory (DFT) as integrated with the WIEN2k code. The volume optimization is performed for different spin configurations to obtain the optimized unit cell structure, using the minimum energy considerations. It is found that the studied systems favor the antiferromagnetic (AFM) structure. Calculated structural parameters are in good agreement with the existing data. Based on their band structures and density of states (DOS), CaMn2P2, SrMn2P2, and SrMn2As2 have a metallic character, while CaMn2As2 is a semiconductor with a narrow band gap of 0.1161 eV on using GGA and as metallic when GGA+U is employed. The density of states diagrams show that the Mn-3d state contributes majorly to the valence band and the lower part of the conduction band. From stable geometries of XMn2Y2 compounds, it is evident that the Mn atoms are coupled antiferromagnetically in all the compounds. The large value of TC for CaMn2As2 shows strong correspondence among the magnetic atoms. Owing to their suitable magnetic characteristics, these compounds can be used in applications such as Colossal magnetoresistance (CMR) or Giant magnetoresistance (GMR), single-molecule magnets, read heads, spin filters, spin valves, magnetic sensors, and in spintronics applications. Furthermore, temperature and pressure dependence of thermodynamic properties of these materials have been examined in the ranges (0–800 K) and (0–18 GPa), respectively.