Neutron powder diffraction studies of magnetic order in non-centrosymmetric oxides Ni4Nb2O9

Among corundum niobates, Ni4Nb2O9 is the only compound that lacks the centre of symmetry in its crystal structure. Although previous work confirms that the Ni2+ ions occupy two different crystallographic sites, it fails to provide a clear understanding of the magnetic properties of this compound. The compound shows compensated magnetic moment followed by the magnetization reversal. Our x-ray diffraction and absorption spectroscopy indicate a mixed charge state in Nickel and the signature of charge ordering. To understand the exact role of two different Ni sites towards the magnetically ordered state, we propose to perform a neutron powder diffraction experiment down to 10 K. This will provide us with the magnetic structure and the origin of magnetization reversal. Additionally, it will help us to determine any structural anomaly associated with the charge ordering transition.