Temperature-dependent resistivity and anomalous Hall effect in NiMnSb from first principles

David Wagenknecht,Jairo Sinova,Zdeněk Kašpar,Tomáš Jungwirth,Ilja Turek,Libor Šmejkal,Karel Carva,Josef Kudrnovský

doi:10.1103/physrevb.99.174433

Abstract

We present implementation of the alloy analogy model within fully relativistic density-functional theory with the coherent potential approximation for a treatment of nonzero temperatures. We calculate contributions of phonons and magnetic and chemical disorder to the temperature-dependent resistivity, anomalous Hall conductivity (AHC), and spin-resolved conductivity in ferromagnetic half-Heusler NiMnSb. Our electrical transport calculations with combined scattering effects agree well with experimental literature for Ni-rich NiMnSb with 1--2% Ni impurities on Mn sublattice. The calculated AHC is dominated by the Fermi surface term in the Kubo-Bastin formula. Moreover, the AHC as a function of longitudinal conductivity consists of two linear parts in the Ni-rich alloy, while it is nonmonotonic for Mn impurities. We obtain the spin polarization of the electrical current $P>90%$ at room temperature and we show that $P$ may be tuned by chemical composition. The presented results demonstrate the applicability of an efficient first-principles scheme to calculate temperature dependence of linear transport coefficients in multisublattice bulk magnetic alloys.

Highlights

Microscopic description of finite temperature effects in magnetic materials represents a longstanding challenge for ab initio theory despite tremendous progress over past 20 years in numerically demanding calculation of small quantities such as magnetocrystalline anisotropies or anisotropic magnetoresistance[1,2,3,4]
One possibility of ab initio description of electronic coupling to magnons and phonons is based on the alloy analogy model (AAM) which was recently employed to calculate electrical conductivity and the anomalous Hall conductivity (AHC) in elemental ferromagnets and binary alloys[5,6]
The main conclusions are: (i) The calculated temperature dependence of the longitudinal conductivity is dominated by the phonon contribution and it is in agreement with experimental literature

Summary

Introduction

Microscopic description of finite temperature effects in magnetic materials represents a longstanding challenge for ab initio theory despite tremendous progress over past 20 years in numerically demanding calculation of small quantities such as magnetocrystalline anisotropies or anisotropic magnetoresistance[1,2,3,4]. A simulation of electrical transport coefficients at room temperature, that are important for spintronics, requires coupling of electrons to phonons or magnons. One possibility of ab initio description of electronic coupling to magnons and phonons is based on the alloy analogy model (AAM) which was recently employed to calculate electrical conductivity and the anomalous Hall conductivity (AHC) in elemental ferromagnets and binary alloys[5,6]. Spin fluctuations or the magnetic orientational disorder can be treated analogically in a similar way. The limiting case of full spin disorder is called the disordered local moment (DLM) state[7,8,9,10] and describes the paramagnetic state above the Curie temperature

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Conclusion