Possible Half Metallic Antiferromagnetism in a Double Perovskite Material with Strong Spin-Orbit Couplings

TL;DR

This paper predicts that a double perovskite material, Pr$_2$MgIrO$_6$, can exhibit half metallic antiferromagnetism due to strong spin-orbit coupling and electron interactions, with potential spintronics applications.

Contribution

It demonstrates the possibility of half metallic antiferromagnetism in a double perovskite through first-principles calculations, highlighting the role of SOC and Coulomb interactions.

Findings

Pr$_2$MgIrO$_6$ is a magnetic Mott-Hubbard insulator influenced by SOC and Coulomb interactions.

Gradual Sr substitution induces half metallic states with different magnetic orders.

Large exchange splitting enables half metallicity despite strong SOC.

Abstract

Using the first-principles density functional approach, we investigate a material Pr$_2$MgIrO$_6$ (PMIO) of double perovskite structure synthesized recently. According to the calculations, PMIO is a magnetic Mott-Hubbard insulator influenced by the cooperative effect of spin-orbit coupling (SOC) and Coulomb interactions of Ir-5$d$ and Pr-4$f$ electrons, as well as the crystal field. When Pr is replaced with Sr gradually, the system exhibits half metallic (HM) states desirable for spintronics applications. In [Pr$_{2-x}$Sr$_x$MgIrO$_6$]$_2$, HM antiferromagnetism (HMAFM) with zero spin magnetization in the unit cell is obtained for $x=1$, whereas for $x=0.5$ and 1.5 HM ferrimagnetism (HMFiM) is observed with $\mu_{\rm tot}=3\mu_{\rm B}$ and $\mu_{\rm tot}=-3\mu_{\rm B}$ per unit cell respectively. It is emphasized that the large exchange splitting between spin-up and spin-down bands at the Fermi level makes the half metallicity possible even with strong SOC.