Weak ferromagnetic insulator with huge coercivity in monoclinic double perovskite La2CuIrO6

TL;DR

This study uncovers a new monoclinic phase of La2CuIrO6 that exhibits weak ferromagnetism with extremely high coercivity, combining experimental and theoretical methods to reveal its magnetic and structural properties.

Contribution

The paper reports the discovery of a new P21/n polymorph of La2CuIrO6 and characterizes its weak ferromagnetism and high coercivity through combined experimental and density functional theory analyses.

Findings

Identified a new P21/n polymorph of La2CuIrO6.

Observed weak ferromagnetic transition at 62 K with high coercivity (~12 kOe).

Confirmed the Mott insulating ferromagnetic state via first-principles calculations.

Abstract

Insulating ferromagnets with high TC are required for many new magnetic devices. More complexity arises when strongly correlated 3d ions coexist with strongly spin-orbit coupled 5d ones in a double perovskite. Here, we perform the structural, magnetic, and density functional theory study of such double perovskite La2CuIrO6. A new P21/n polymorph is found according to the comprehensive analysis of x-ray, Raman scattering and phonon spectrum. The magnetization reveals a weak ferromagnetic (FM) transition at TC = 62 K and short range FM order in higher temperature range. A huge coercivity is found as high as HC~11.96 kOe at 10K, which in combination with the negative trapped field results in the magnetization reversal in the zero field cooling measurement. The first principle calculations confirm the observed FM state and suggest La2CuIrO6 of this polymorph is a Mott insulating ferromagnet assisted by the spin-orbit coupling.