Magnetic order and spin-orbit coupled Mott state in double perovskite (La${}_{1-x}$Sr${}_x$)${}_2$CuIrO${}_6$

Abstract

Double-perovskite oxides that contain both 3d and 5d transition metal elements have attracted growing interest as they provide a model system to study the interplay of strong electron interaction and large spin-orbit coupling (SOC). Here, we report on experimental and theoretical studies of the magnetic and electronic properties of double-perovskites (La${}_{1-x}$Sr${}_x$)${}_2$CuIrO${}_6$ ($x$ = 0.0, 0.1, 0.2, and 0.3). The undoped La${}_2$CuIrO${}_6$ undergoes a magnetic phase transition from paramagnetism to antiferromagnetism at T${}_N$ $\sim$ 74 K and exhibits a weak ferromagnetic behavior below $T_C$ $\sim$ 52 K. Two-dimensional magnetism that was observed in many other Cu-based double-perovskites is absent in our samples, which may be due to the existence of weak Cu-Ir exchange interaction. First-principle density-functional theory (DFT) calculations show canted antiferromagnetic (AFM) order in both Cu${}^{2+}$ and Ir${}^{4+}$ sublattices, which gives rise to weak ferromagnetism. Electronic structure calculations suggest that La${}_2$CuIrO${}_6$ is an SOC-driven Mott insulator with an energy gap of $\sim$ 0.3 eV. Sr-doping decreases the magnetic ordering temperatures ($T_N$ and $T_C$) and suppresses the electrical resistivity. The high temperatures resistivity can be fitted using a variable-range-hopping model, consistent with the existence of disorders in these double-pervoskite compounds.

Submitted; updated and added references in v2

Cited by in corpus (1)

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