Structural, magnetic and electrical properties of strontium-doped neodymium nickelate

We have measured some of the physical properties of the Nd 2−x Sr x NiO 4+y family below room temperature and find a complicated system in which orthorhombic lattice distortion, oxygen stoichiometry, resistivity and magnetic susceptibility change with strontium doping. As the strontium concentration is increased the materials become stoichiometric and tetragonal without reduction and the conductivity of the samples increases although remaining semiconducting. Some compounds demonstrate an unusual low temperature susceptibility which is either temperature independent or falls slightly below ~ 15 K.