Synthesis, Structure and Magnetic Properties of NiFe3O5

A new CaFe3O5-type phase NiFe3O5 (orthorhombic Cmcm symmetry, cell parameters a = 2.89126(7), b = 9.71988(21) and c = 12.52694(27) Å) has been synthesised under pressures of 12-13 GPa at 1200 C. NiFe3O5 has an inverse cation site distribution and reveals an interesting evolution from M2+(Fe3+)2Fe2+O5 to Fe2+(M2+0.5Fe3+0.5)2Fe3+O5 distributions over three distinct cation sites as M2+ cation size decreases from Ca to Ni. Magnetic susceptibility measurements show successive transitions at 275, ∼150, and ∼20 K and neutron diffraction data reveal a series of at least three spin-ordered phases with evolving propagation vectors k = [0 0 0] → [0 k y 0] → [1/2 1/2 0] on cooling. The rich variety of magnetically ordered phases in NiFe3O5 likely results from frustration of Goodenough-Kanamori exchange interactions between the three spin sublattices, and further interesting magnetic materials are expected to be accessible within the CaFe3O5-type family