Neutron Diffraction study of a frustrated garnet compound Mn3CrGaGe3O12

In our recent work, we reported a detailed study of a frustrated garnet compound Mn3Cr2Ge3O12, where the Cr3+ and Mn2+ sub-lattices order independently at TN1 ≃ 4.6 K and TN2 ≃ 2.7 K, respectively. However, the interaction between the sub-lattices was not understood very well. In order to have a better understanding of the spin-lattice, we diluted the Cr site by non-magnetic Ga (Mn3CrGaGe3O12) assuming that it will impact both the orderings as well as the inter-sublattice interactions. From the magnetization and heat capacity data, it is clearly evident that Mn3CrGaGe3O12 has two transitions at TN1 ≃ 3.9 K and TN2 ≃ 1.8 K similar to Mn3Cr2Ge3O12. In a magnetic field of about 1 T, TN2 is completely suppressed while TN1 almost remains unperturbed even at 8 T. This behaviour is completely opposite to that observed in Mn3Cr2Ge3O12 where TN1 is completely suppressed at 1 T while TN2 remains unchanged even at 9 T. Hence, it is interesting to see which transition is affected due to non-magnetic substitution at the Cr3+ site and how the inter-sublattice interactions play the role in stabilizing the ground state and the field induced states. In order to have a clear understanding of the ground state and magnetic interactions in this compound, we propose to do powder neutron diffraction experiments in zero-field at several temperatures below and above TN1 and TN2 in WISH spectrometer.