Half Metal Transition Driven by Doping Effects in Osmium Double Perovskite

TL;DR

This study uses first-principles calculations to explore how doping in osmium double perovskites induces a transition to half-metallic states, with potential applications in spintronics.

Contribution

It demonstrates that doping Ca$_2$FeOsO$_6$ with Ni induces half-metallic ferrimagnetic and antiferromagnetic states, revealing a new route to engineer spintronic materials.

Findings

Ni doping induces half-metallic ferrimagnetism at x=0.5

Full Ni substitution results in half-metallic antiferromagnetism

Half metallicity persists even with spin-orbit coupling effects

Abstract

Using the first-principles density functional approach, we investigate Ca$_2$FeOsO$_6$, a material of double perovskite structure synthesized recently. According to the calculations, Ca$_2$FeOsO$_6$ is a ferrimagnetic Mott-insulator influenced by the cooperative effect of spin-orbit coupling (SOC) and Coulomb interactions of Fe-3$d$ and Os-5$d$ electrons, as well as the crystal field. When Fe is replaced with Ni, the system exhibits half metallic (HM) states desirable for spintronic applications. In [Ca$_2$Fe$_{1-x}$Ni$_x$OsO$_6$]$_2$, HM ferrimagnetism is observed with $\mu_{\rm tot}=2\mu_{\rm B}$ per unit cell for doping rate $x=0.5$, whereas HM antiferromagnetism (HMAFM) with nearly zero spin magnetization in the unit cell for $x=1$, respectively. It is emphasized that half metallicity is retained even with SOC effect due to the large exchange-splitting between spin-up and spin-down bands close to the Fermi level.