Observations of ferromagnetic cluster glass and exchange bias behavior in the double perovskite compound La2Cu0.9Cr0.1IrO6

Abstract

La2CuIrO6 is a spin-orbit coupled Mott insulator, and shows a transition to noncollinear antiferromagnetic state from paramagnetic state below 74 K, and further into a weak ferromagnetic state below 54 K. Despite having two different magnetic phases, the La2CuIrO6 compound does not exhibit exchange bias phenomenon. In this present work, we report an experimental investigation on the structural and magnetic properties of the double perovskite compound La2Cu0.9Cr0.1IrO6 through high-resolution synchrotron x-ray diffraction, x-ray absorption near edge structure (XANES), and temperature and field-dependent magnetization measurements. Powder x-ray diffraction analysis reveals that the sample crystallizes in triclinic structure (space group P) alike parent La2CuIrO6 compound, while XANES measurements rule out the possibility of valence state alteration between constituting elements in this sample. Interestingly, La2Cu0.9Cr0.1IrO6 compound is found to exhibit ferromagnetic cluster glass behavior, where field-cooled magnetization undergoes two ferromagnetic transitions. A significant enhancement of ferromagnetic component is also evident from hysteresis loop study, which is likely associated with the electron hopping between J eff = 1/2 pseudospin state of Ir4+ ions and empty eg-orbital of Cr3+ ions. Exclusively, this Cr-doped compound exhibits exchange bias effect, which is related to the complex interfacial exchange coupling between the ferromagnetic clusters and the host antiferromagnetic matrix.