Comparative Raman scattering study of Ba3MSb2O9 (M=Zn, Co and Cu)
A. Glamazda1,2, P. Lemmens3,S.-H. Do1, and K.-Y. Choi1
1Department of Physics, Chung-Ang University, Seoul 156-756, Republic of Korea
2B. Verkin Institute for Low Temperature Physics and Engeneering of the National Academy of Sciences of Ukraine 47 Nauky Ave, Kharkiv 61103, Ukraine
3Institute for Condensed Matter Physics, TU Braunschweig, Braunschweig D-38106, Germany
Received October 11, 2016
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 Ba3ZnSb2O9 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 сonventional magnetic excitations for the equilateral triangular antiferromagnet Ba3CoSb2O9 and a co-existence of spin-orbital liquid and random singlet state for the decorated honeycomb compound Ba3CuSb2O9 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; PACS: 75.45.+j Macroscopic quantum phenomena in magnetic systems; PACS: 78.30.–j Infrared and Raman spectra.