Revealing half-metallicity: Predicting large bandgaps in halogen-based full-Heusler alloys

Abstract

As for spintronic applications, all information is encoded in the spin degree of freedom, so the key issues are the high spin-polarization, large half-metallic (HM) bandgap, large magnetic moment and higher Curie temperature than room temperature. In this paper, we studied halogen based CsYZ2 (Y = V or Cr; Z = F, Cl, Br or I) full-Heusler alloys. Our study reveals that CsVF2, CsVCl2, CsVI2 and CsCrI2 alloys are all HM ferromagnets while remaining alloys exhibits magnetic semiconductor behavior. The electronic structures indicate that these alloys open very large bandgaps in the spin-down channel. Following the Slater-Pauling rule Mt=Zt-16, these alloys exhibit very large total magnetic moments Mt of 4.00 μBf.u. when Y = V and 5.00 μBf.u. when Y = Cr. The high Curie temperatures indicate these alloys are appropriate for spintronic applications at room temperature. Furthermore, the absorption coefficient α(ω) of the CsVF2 alloy is better from other alloys in the visible region. The maximum ZT = 0.7 is obtained for CsCrBr2 and is an ideal candidate for thermoelectric (TE) applications.

Keywords

• Heusler alloys
• Electronic structures
• Magnetic properties
• Thermoelectric properties
• First-principles