Weak ferromagnetic insulator with huge coercivity in monoclinic double perovskite La₂CuIrO₆

Abstract

Insulating ferromagnets with high T C 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 (DFT) study of such double perovskite La 2 CuIrO 6 . A new P2 1 /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 T C = 62 K and short range FM order in higher temperature range. A huge coercivity is found as high as H C~1 1.96 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 La 2 CuIrO 6 of this polymorph is a Mott insulating ferromagnet assisted by the spin-orbit coupling.

Giant coercivity and spin clusters in high pressure polymorphs of Mn2LiReO6.

“…For instance in Sr 5 Ru 4.1 O 15 , weak ferromagnetism in combination with the non-zero orbital moment of Ru accounts for the giant coercivity of 12 T at 1.7 K. 2 In the double perovskites (DPv) La 2 CuIrO 6 , 3 La 2 Ni 1. 19 Os 0.81 O 6 4 and Lu 2 NiIrO 6 5 the combination of magnetocrystalline anisotropy along with frustration or defects was found to favor the large H C values of 1.2 T (10 K), 4.1 T (5 K) and 4.8 T (5 K) respectively. Besides the significance of SOC present in the above materials, the pinning of domain walls also plays a crucial role for coercivity enhancement.…”