Half metal-to-metal transition and superior transport response with a very high Curie-temperature in CoFeRuSn: strain regulations

Magnetic materials with a high Curie temperature (<i>T</i> _C) and superior transport behavior are interesting prospects for spintronics and energy conversion devices. The present investigation deals with various traits of the CoFeRuSn quaternary Heusler alloy that were examined under strain (biaxial [110]/hydrostatic [111]) using first-principles calculations. The T1 phase is the ground state configuration relative to the T2 and T3 ones, which is thermodynamically stable owing to a negative formation enthalpy (Δ<i>H</i> _f) and high cohesive energy (<i>E</i> _coh.). It is established that the material exhibits a half-metallic (HM) ferromagnetic (FM) phase holding an energy gap of 0.42 eV in the spin-minority channel. Moreover, Co/Fe/Ru has spin moment of 1.59/3.13/0.53 <i>μ</i> _B with electronic configuration of (3d7) t³ _2g↑t³ _2g↓e¹ _g↑e⁰ _g↓/(3d⁶) t³ _2g↑t³ _2g↓e² _g↑e⁰ _g↓/(4d⁵) t³ _2g↑t² _2g↓e⁰ _g↑e⁰ _g↓ employing which is further confirmed by spin-magnetization density isosurfaces. Exceptionally, a giant <i>T</i> _C of 779 K further enhances its potential for practical realization. Additionally, a large figure of merit (<i>ZT</i>) of 0.93 and n-type carriers indicates a good thermoelectric performance of the material. Surprisingly, a HM-to-metal transition occurs at -4% in both types of compressive strains. Furthermore, <i>ZT</i> reaches ∼1.0 under applied strains, whereas <i>T</i> _C increases by 11% for -5% strain. Hence, this study demonstrates that the CoFeRuSn motif contains multifunctional aspects, enhancing its potential for various applications in spintronics and thermoelectric energy harvesting.