Electronic structure and magnetism in half-Heusler compounds

Abstract

In this paper we have applied the full-potential linearized muffin tin orbital method and the tight-binding linearized muffin tin orbital method to investigate in detail the electronic structure and magnetism of a series of half-Heusler compounds XMZ with X = Fe, Co, Ni, M = Ti, V, Nb, Zr, Cr, Mo, Mn and Z = Sb, Sn. Our detailed analysis of the electronic structure using various indicators of chemical bonding suggests that covalent hybridization of the higher-valent transition element X with the lower-valent transition element M is the key interaction responsible for the formation of the d-d gap in these systems. However, the presence of the sp-valent element is crucial to provide stability to these systems. The influence of the relative ordering of the atoms in the unit cell on the d-d gap is also investigated. We have also studied in detail some of these systems with more than 18 valence electrons which exhibit novel magnetic properties, namely half-metallic ferro-and ferrimagnetism. We show that the d-d gap in the paramagnetic state, the relatively large X-Sb hybridization and the large exchange splitting of the M atoms are responsible for the half-metallic property of some of these systems.

Exchange interactions and temperature dependence of magnetization in half-metallic Heusler alloys

“…12 Up to now the main body of the theoretical studies was devoted to the properties of the half-metallic gap. 13 Recently, Chioncel and collaborators studied the influence of the correlation effects on the electron structure of CrAs.…”

New High-TcHalf-Heusler Ferromagnets NiMnZ (Z=Si, P, Ge, As)

“…Theoretically, the attempts to replace Ni (or Mn) of NiMnSb by other metals such as Fe, Co, etc. give a halfmetallic picture in the band structure of some alloys [1,7] such as FeMnSb, CoMnSb and FeCrSb, etc.…”

Thermoelectric and Thermophysical Properties of TiCoSb-ZrCoSb-HfCoSb Pseudo Ternary System Prepared by Spark Plasma Sintering

“…It has been known that these compounds with 18 valence electrons per unit cell are semiconductors possessing the narrow gap and sharp slope of the density of states around the Fermi level. [1][2][3][4][5] The theoretically calculated band gap energy of TiCoSb (0.95, 1) 0.82 eV 5) ) is larger than that of the similar material TiNiSn (0.42 eV, 1) 0.51 2) ). So, TiCoSb is expected to have a larger thermoelectric power S. From the literatures, [6][7][8][9][10][11] TiCoSb has a negative thermoelectric power.…”