Comparative Raman scattering study of Ba3MSb2O9 (M=Zn, Co and Cu)

Abstract

Raman spectroscopy is combined with lattice dynamic calculations to investigate the magnetic and structural properties of the 6H-perovskite compounds Ba3MSb2O9 (M = Zn, Co and Cu). Unlike the nonmagnetic Ba3MSb2O9 compound, the magnetic counterparts Ba3MSb2O9 (M = Co and Cu) show both lattice anomalies for temperatures below 100 K and develop highly correlated spin states below 50 K. This is ascribed to an instability of conventional magnetic excitations for the equilateral triangular antiferromagnet Ba3MSb2O9 and a coexistence of spin-orbital liquid and random singlet state for the decorated honeycomb compound Ba3MSb2O9 containing a nearly identical volume fraction of hexagonal and orthorhombic phases. Our results demonstrate that Ba3MSb2O9 provides a rich reservoir for hosting diverse magnetic and structural phases as a function of the metal ion M. PACS: 63.20.-e Phonons in crystal lattices; 75.45.+j Macroscopic quantum phenomena in magnetic systems; 78.30.-j Infrared and Raman spectra. © A. Glamazda, P. Lemmens, S.-H. Do, and K.-Y. Choi, 2017.