The structure and paramagnetism of Ni₃Nb

Abstract

A single crystal of Ni3Nb has been investigated with X-ray diffraction to determine the structure, and with bulk magnetic measurements and neutron polarization analysis to characterize the enhanced paramagnetic behaviour. The structure has been confirmed to be ordered and orthorhombic, having the space group Pmmn, and with lattice constants a=5.114 AA, b=4.244 AA, and c=4.53 AA. The magnetization results do not produce straight Arrott plots and attempts to fit the magnetization to a model with a Langevin function describing local moments, in addition to a band component, yield local moments that vary with temperature. The paramagnetic neutron scattering agrees with the measured static susceptibility in the small-scattering-vector limit suggesting that the energy width of the scattering is much less than the energy of the incident neutrons (6 meV). The scattering vector dependence of the paramagnetic scattering can be fitted by a Lorentzian that is consistent with a paramagnetic enhancement factor of 40-50 assuming predominant first-neighbour exchange.