We report the structural and magnetic properties of the 4d (M = Rh) based and 5d ( M = Ir) based systems Ba3MxTi3-xO9 ( nominally x = 0.5, 1). The studied compositions were found to crystallize in a hexagonal structure with the centrosymmetric space group P6(3)/mmc. The structures comprise of A(2)O(9) polyhedra [ with the A site ( possibly) statistically occupied by M and Ti] in which pairs of transition metal ions are stacked along the crystallographic c axis. These pairs form triangular bilayers in the ab plane. The magnetic Rh and Ir ions occupy these bilayers, diluted by Ti ions even for x = 1. These bilayers are separated by a triangular layer which is dominantly occupied by Ti ions. From magnetization measurements we infer strong antiferromagnetic couplings for all of the materials but the absence of any spin-freezing or spin-ordering down to 2 K. Further, specific heat measurements down to 0.35 K show no sign of a phase transition for any of the compounds. Based on these thermodynamic measurements we propose the emergence of a quantum spin liquid ground state for Ba(3)Rh(0.)5Ti(2.5)O(9), and Ba3Ir0.5Ti2.5O9, in addition to the already reported Ba3IrTi2O9.
Pedro Miguel Nunes Pereira de Almeida Reis, Michael Christopher Gomez
Duncan Thomas Lindsay Alexander, Bernat Mundet, Jean-Marc Triscone