First-principles calculations on the spin anomalous Hall effect of ferromagnetic alloys

TL;DR

This study uses first-principles calculations to analyze the spin anomalous Hall effect in ferromagnetic alloys, revealing how different compositions influence spin Hall conductivity and polarization.

Contribution

It provides a theoretical investigation of the spin anomalous Hall conductivity in L1$_0$-type alloys using density functional theory and linear response, highlighting the role of valence electrons and electronic states.

Findings

FePt has a small SAHC compared to AHC, with low polarization.

SAHC increases with more valence electrons, with CoPt and NiPt showing larger values.

Negative spin-down contributions cause large SAHC and polarization in CoPt and NiPt.

Abstract

The spin anomalous Hall effect (SAHE) in ferromagnetic metals, which can generate spin-orbit torque to rotate the magnetization of another ferromagnetic layer through a non-magnetic spacer in magnetic junctions, has attracted much attention. We theoretically investigated the spin anomalous Hall conductivity (SAHC) of the L1$_0$-type alloys $X$Pt($X$=Fe,Co,Ni) on the basis of first-principles density functional theory and linear response theory. We found that the SAHC of FePt is much smaller than the anomalous Hall conductivity (AHC), leading to very small polarization for the anomalous Hall effect $\zeta$=SAHC/AHC of around 0.1. On the other hand, the SAHC increases with increasing number of valence electrons($N_{\rm v}$), and CoPt and NiPt show relatively large values of $|\zeta|$, greater than 1. The negative contribution of the spin-down-down component of AHC is the origin of the large SAHC and $\zeta$ in CoPt and NiPt, which is due to the anti-bonding states of Pt around the Fermi level in the minority-spin states.