Ferrimagnetism and strain-tunable half-metallicity in Cr2CoZ (Z = P, As) inverse Heusler alloys

Abstract

The electronic structure of inverse Heusler alloys can be tuned through the choice of the main- group element and lattice strain. The closely related inverse Heusler compounds Cr2CoP and Cr2CoAs provide a convenient model system for examining the influence of these two factors on their electronic structure and related physical properties. Using first-principles calculations, we investigate the structural, electronic, magnetic, mechanical, vibrational, thermodynamic, and optical properties of these compounds, together with the evolution of their electronic structure under lattice strain. Both compounds adopt the inverse Heusler (XA) structure with a ferrimagnetic ground state and a total magnetic moment of approximately 2.00 μB per formula unit. Cr2CoP exhibits intrinsic half- metallicity, with the minority-spin band gap increasing from 0.67 eV within GGA–PBE to 0.95 eV with SCAN. In contrast, Cr2CoAs lies close to the half-metallic limit at equilibrium but becomes fully half-metallic under moderate compressive strain, with the minority-spin band gap reaching 0.51 eV at 2% strain. The calculated elastic constants and phonon dispersion relations confirm the mechanical and dynamical stability of both compounds, while their thermodynamic properties exhibit smooth temperature dependence without any indication of structural instability up to 800 K. The calculated optical spectra exhibit strong visible-ultraviolet absorption and high infrared reflectivity, indicating potential for optoelectronic applications. The present results confirm the intrinsic half-metallicity of Cr2CoP and identify moderate compressive strain as an effective route to achieving half-metallicity in Cr2CoAs. More broadly, these findings demonstrate that both the main-group element and lattice strain offer effective means of tuning the half-metallic electronic structure of inverse Heusler Cr2CoZ compounds.