Ammonium–cobalt–nickel phosphates, NH4[Co1−xNixPO4]·H2O

Abstract

The ammonium–cobalt–nickel phosphates, NH4[Co1−xNixPO4]·H2O (x=0.00, 0.34, 0.59, 0.70, 1.00), and the deuterated forms, ND4[Co1−xNixPO4]·D2O (x=0.00, 0.38, 0.48, 0.69, 0.85), have been synthesized under mild hydrothermal conditions and characterised using X-ray and neutron diffraction, chemical and thermal analysis, and magnetic measurements. Their crystal structures, including hydrogen positions, were determined by Rietveld refinement using single-crystal X-ray and neutron powder diffraction data. The space group of these orthorhombic crystals modifies as a function of their composition. The magnetic susceptibility and magnetization measurements of these ammonium–cobalt–nickel phosphates show antiferromagnetic behaviour, and the Neel temperature evolves from 5.5 K (x=0.00) up to 13.2 K (x=1.00).