Hafnium based ferromagnetic half metals for spintronic and thermoelectric applications — Materials Computation

In this study, we investigate the spintronic and thermoelectric properties of half-Heusler alloys $HfMnZ$ ($Z=Sn,Sb,Bi$) using density functional theory. Initially, we have optimized the cubic structure of the considered crystal alloys for various magnetic phases. Through calculations, we obtained that minimum ground state energy in ferro-magnetic phase. Following we have confirmed both the structural and mechanical stability of the alloys. Using generalized gradient approximation, we studied the electronic properties of the alloys $HfMnZ$ ($Z=Sn,Sb,Bi$) and we obtained the band gap in spin up channel. For $HfMnSn$, the calculated band gap value is 0.77 eV, 1.09 eV for $HfMnSb$ and the band gap value of $HfMnBi$ is 0.29 eV in spin up channel. The presence of band gap only in the spin up channel confirms the half-metallic nature of the considered alloys. Also, the band gap are indirect in nature for $HfMnSn$ and $HfMnSb$ alloys whereas for $HfMnBi$ the direct band gap is observed. The positive integer total magnetic moment values of $HfMnZ$ ($Z=Sn,Sb,Bi$) confirms the ferro magnetic nature of the materials. We have also studied the transport properties of the alloys $HfMnZ$ ($Z=Sn,Sb,Bi$) with the $ZT$ values 0.52, 0.6 and 0.29 respectively. Our results shows that the half-Heusler alloys $HfMnZ$ ($Z=Sn,Sb,Bi$) are suitable for spintronic and thermoelectric applications.