Thermal evolution of magnetic and crystal structures of quaternary perovskites Ba4MRu3O12 (M = Li, Na, Mg, Zn)

Orbital molecules represent a quantum state where directly bonded clusters of orbitally ordered atoms are formed. They are often found in systems hosting dimers/trimers and we propose to investigate a class of such materials: Ba4MRu3O12 (M=Li, Na, Mg, Zn). The physics here is dictated by the interaction within, and between Ru2O9 dimers and RuO6 octahedra, which make up the magnetic (and electronic) building blocks of these inherently frustrated systems. We have synthesized a few of these yet un-investigated systems and found that their phase diagram shows a cascade of phase transitions as a function of temperature. Investigation of these systems using neutron powder diffraction will provide crucial information on the temperature dependent evolution of their crystal and magnetic structures, as well as the driving mechanisms behind the observed transitions.