Inducing magnetism in thermoelectric half-Heusler alloy NbCoSb through doping of Co/Mn metal for spin-caloritronics applications

Abstract

Recent progress in spin caloritronics has boosted exploration of materials for their application in this novel field. Heusler alloys which were being hailed as thermoelectric and magnetic materials have seen uprise for their suitable properties however lack of studies featuring good coupling between magnetic and thermoelectric properties have seen little impact in the field of spin-caloritronics. Present work explored doping of transition metal in a thermoelectric half-Heusler alloys NbCoSb on Nb site to induce spin-polarization and spin-dependent transport properties. Co (Mn) doping results in 98.09% (19.38%) negative spin polarization and 0.51 μB/f.u. (1.98 μB/f.u.) magnetic moment. Magnetic exchange parameter shows presence of long range RKKY-type interaction in Co and Mn doped NbCoSb. On one-hand, doping of Co and Mn in NbCoSb suppressed the electronic transport properties whereas, on the other hand spin dependent Seebeck effect is introduced. The synergistic effect of magnetic and thermoelectric properties in non-magnetic NbCoSb via doping of Mn and Co shows large variation in the value of Seebeck coefficient, electrical conductivity and electronic thermal conductivity with flipping of spin-directions suggests Co rich NbCoSb as a promising candidate for spin-caloritronics application.