Etude des propriétés structurales, électroniques, magnétiques et thermoélectriques de quelques alliages demi-métalliques

Abstract

Quaternary Heusler materials exhibiting half-metallicity (HM) and a high critical temperature TC are emerging as promising candidates for spintronic devices. Density functional theory is used to study the structural properties, electronic structure of the new quaternary Heusler compounds PrCoCrZ (Z = Al, Ga), PrCoMnZ (Z = Ga, In), and NdCoMnZ (Z = Al, In). The total energies as a function of volume for the six materials were calculated to formulate the characteristics of the ground state. We used TB-MBJ to estimate the band structures and densities of states. The results confirm that the alloys are half-metallic with considerable half-metallic gaps of 0.61 eV, 0.58 eV, 0.56 eV, 0.51 eV, 0.48 eV, and 0.48 eV for PrCoCrAl, PrCoCrGa, PrCoMnGa, PrCoMnIn, NdCoMnAl, and NdCoMnIn, respectively. All the alloys have magnetic moments that are integers (5, 6, and 7 μB) and satisfy the Pauli rule Mtot=Ztot-18. Our calculation of the Curie temperature TC showed that the values range from 928 to 1290 K. The magnetic moments as a function of the lattice constant were also calculated for all materials. The thermoelectric properties of all materials are acquired using the BoltzTraB code based on the semi-classical Boltzmann transport theory. The investigation of thermoelectric characteristics showed that all alloys exhibit higher electrical conductivities and lower thermal conductivities.