Magnetism and spin-orbit coupling in Ir-based double perovskites La$_(2-x$Sr$_x$CoIrO$_6$

TL;DR

This study investigates the magnetic moments and spin-orbit effects in Ir-based double perovskites La$_{2-x}$Sr$_x$CoIrO$_6$ using x-ray magnetic circular dichroism, revealing how Ir's magnetic behavior varies with oxidation state and structure.

Contribution

It provides new insights into the magnetic coupling and spin-orbit interactions in Ir-based double perovskites, highlighting the role of oxidation state and structure in magnetic moment induction.

Findings

Ir$^{4+}$ couples antiferromagnetically with Co$^{2+}$ in La$_2$CoIrO$_6$

Ir$^{5+}$ exhibits a paramagnetic moment with negligible orbital contribution in Sr$_2$CoIrO$_6$

Spin-orbit coupling influences the magnetic moments and susceptibility in these materials.

Abstract

We have studied Ir spin and orbital magnetic moments in the double perovskites La$_{2-x}$Sr$_x$CoIrO$_6$ by x-ray magnetic circular dichroism. In La$_2$CoIrO$_6$, Ir$^{4+}$ couples antiferromagnetically to the weak ferromagnetic moment of the canted Co$^{2+}$ sublattice and shows an unusually large negative total magnetic moment (-0.38\,$\mu_{\text B}$/f.u.) combined with strong spin-orbit interaction. In contrast, in Sr$_2$CoIrO$_6$, Ir$^{5+}$ has a paramagnetic moment with almost no orbital contribution. A simple kinetic-energy-driven mechanism including spin-orbit coupling explains why Ir is susceptible to the induction of substantial magnetic moments in the double perovskite structure.