Crystal growth and magnetic characterization of a tetragonal polymorph of NiNb2O6

A previously unidentified polymorph of nickel niobate, NiNb2O6, was grown and stabilized in single crystalline form using an optical floating zone furnace. Key parameters of the growth procedure involved use of a slight excess of NiO (1.2% by mol), an O2 atmosphere and a growth rate of 25mm/h. The resulting boule consisted of a polycrystalline exterior shell of the columbite structure – columbite is the thermodynamically stable form of NiNb2O6 …