Solution precursor synthesis and magnetic properties of Eu1−xCaxTiO3

Europium titanate, EuTiO3, is a paraelectric/antiferromagnetic cubic perovskite with TN=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 Eu2+ with the smaller Ca2+ cation as a mechanism to tune the magnetic properties of EuTiO3. A modified sol–gel process was used to form homogeneously mixed precursors containing Eu3+, Ca2+, and Ti4+, and reductive annealing was used to transform these precursors into crystalline powders of Eu1−xCaxTiO3 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 Eu1−xCaxTiO3 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 TN decreasing from 5.4 K in EuTiO3 to 2.6 K in Eu0.40Ca0.60TiO3. No antiferromagnetic ordering above 1.8 K was detected in samples with x>0.60.

Twelve members of the Eu1−xCaxTiO3 solid solution (0≤x≤1) were synthesized by first forming a homogeneously mixed precursor using a modified sol–gel process, followed by reductive annealing. Samples with x≤0.60 are antiferromagnetic, with TN decreasing as the level of calcium substitution increases.Figure optionsDownload as PowerPoint slide