Diffuse Magnetic Scattering in GeNi$_{2}$O$_{4}$

The cubic spinel GeNi$_{2}$O$_{4}$, in which the spin-1 Ni$^{2+}$ ions are located at the vertices of a lattice of corner-sharing tetrahedra, exhibits interesting magnetic properties. For example, GeNi$_{2}$O$_{4 }$has two N\'{e}el transitions (T$_{N1}$ = 12.1 K and T$_{N2}$ = 11.4 K) that are not associated with any obvious structural phase transition. In the past we have reported the results of magnetic susceptibility, heat capacity, synchrotron x-ray powder diffraction, and neutron powder diffraction measurements for this material. In this talk we will describe the results of diffuse magnetic scattering measurements of the magnetic correlations in GeNi$_{2}$O$_{4}$ made at temperatures above and below T$_{N1}$ and T$_{N2}$. The samples were single crystals grown by the traveling solvent floating zone technique at AIST. The measurements were made using the PRISMA spectrometer at ISIS and a triple-axis spectrometer at NIST.