Spectral signatures of thermal spin disorder and excess Mn in half-metallic NiMnSb

Authors

Kirill D. Belashchenko, University of Nebraska-LincolnFollow
Jeevaka Weerasinghe, University of Nebraska-Lincoln
Sai Mu, University of Nebraska-LincolnFollow
Bhalchandra S. Pujari, University of Nebraska–LincolnFollow

Document Type

Article

Date of this Version

2015

Citation

PHYSICAL REVIEW B 91, 180408(R) (2015)

Comments

©2015 American Physical Society

Abstract

Effects of thermal spin disorder and excessMn on the electronic spectrum of half-metallic NiMnSb are studied using first-principles calculations. Temperature-dependent spin disorder, introduced within the vector disordered local moment model, causes the valence band at the Γ point to broaden and shift upwards, crossing the Fermi level and thereby closing the half-metallic gap above room temperature. The spectroscopic signatures of excess Mn on the Ni, Sb, and empty sites (Mn_Ni, Mn_Sb, andMn_E) are analyzed. Mn_Ni is spectroscopically invisible. The relatively weak coupling of Mn_Sb and Mn_E spins to the host strongly deviates from the Heisenberg model, and the spin of MnE is canted in the ground state. While the half-metallic gap is preserved in the collinear ground state of Mn_Sb, thermal spin disorder of the weakly coupled Mn_Sb spins destroys it at low temperatures. This property of MnSb may be the source of the observed low-temperature transport anomalies.