A neutron diffraction and 170Yb Mössbauer investigation of the perovskite ytterbium titanium oxide

A phase with the perovskite structure (Pbnm) and a composition YbTiO_2.95 has been prepared by a high-temperature carbothermic method. Neutron diffraction shows a colinear ferrimagnetic structure at 7 K with Yb and Ti moments antiparallel along the c-axis of the orthorhombic cell and an Yb moment of 1.8(3)μ_B. ¹⁷⁰Yb Mössbauer measurements find a more precise and accurate value of 2.0(1)μ_B from the maximum hyperfine field. From the temperature dependence of the hyperfine field a T_c = 42(1) K is found. The Yb sublattice magnetization below T_c follows a Brillouin function. At low temperature a distribution of hyperfine fields is observed which is attributed to a random distribution of defects surrounding the Yb sites. The magnetic structure is discussed in relation to possible values for the crystal field parameters, especially B²₀.