Solution precursor synthesis and magnetic properties of Eu 1−xCa xTiO 3

Abstract

Europium titanate, EuTiO 3, is a paraelectric/antiferromagnetic cubic perovskite with T N=5.5 K. It is predicted that compressive strain could induce simultaneous ferroelectricity and ferromagnetism in this material, leading to multiferroic behavior. As an alternative to epitaxial strain, we explored lattice contraction via chemical substitution of Eu 2+ with the smaller Ca 2+ cation as a mechanism to tune the magnetic properties of EuTiO 3. A modified sol–gel process was used to form homogeneously mixed precursors containing Eu 3+, Ca 2+, and Ti 4+, and reductive annealing was used to transform these precursors into crystalline powders of Eu 1− x Ca x TiO 3 with x=0.00, 0.05, 0.10, 0.15, 0.25, 0.35, 0.50, 0.55, 0.60, 0.65, 0.80, and 1.00. Powder XRD data indicated that a continuous Eu 1− x Ca x TiO 3 solid solution was readily accessible, and the lattice constants agreed well with those predicted by Vegard's law. SEM imaging and EDS element mapping indicated a homogeneous distribution of Eu, Ca, and Ti throughout the polycrystalline sample, and the actual Eu:Ca ratio agreed well with the nominal stoichiometry. Measurements of magnetic susceptibility vs. temperature indicated antiferromagnetic ordering in samples with x≤0.60, with T N decreasing from 5.4 K in EuTiO 3 to 2.6 K in Eu 0.40Ca 0.60TiO 3. No antiferromagnetic ordering above 1.8 K was detected in samples with x>0.60.