Determination of magnetic ground state in the trimer based mixed valent hexagonal perovskite ruthenate Ba4NbRu3O12 using powder neutron diffraction

The trimer based 12L-hexagonal quadrupole perovskites Ba4MM’3O12(M=di, tri, tetra, and pentavalent cation; M’=heavy transition metal Ru, Rh, and Ir) serve as a potential avenue for various intriguing magnetic ground states due to a delicate balance between spin-orbit coupling (SOC) of 4d/5d transition metals, crystal field splitting, intra & inter-trimer magnetic exchange interactions, and geometric frustration. Ba4NbRu3O12 has recently been reported to be a geometrically frustrated Mott insulator, showing apparent quantum spin liquid like signature in both the high-field dc magnetization and heat capacity data, as well as T-linear contribution to the magnetic specific heat at very low-T. However, appearance of a ZFC and FC peak around 4 K in the 100 Oe susceptibility data, and a ZFC/FC irreversibility together with a broad hump-like anomaly in the magnetic specific heat in the 7-10 K temperature range, indicate a possible magnetic ordering. To shed light on the ground state of this material, we are going to undertake neutron powder diffraction measurements using the high-resolution cold neutron diffractometer WISH