Long-range and local crystal structures of the S⁢r1−𝑥⁢C⁢a𝑥⁢Ru⁢O3 perovskites

Abstract

The crystal structures of the S⁢r1−𝑥⁢C⁢a𝑥⁢Ru⁢O3⁡(0≤𝑥≤1) perovskites are investigated using both long-range and local structural probes. High-resolution synchrotron powder x-ray-diffraction characterization at ambient temperature shows that the materials have orthorhombic long-range crystal structures to high precision, and we support previous work showing that C⁢a2+ substitution for S⁢r2+ primarily changes the tilting of rigid corner-sharing Ru⁢O6 octahedra at their shared oxygen vertices. X-ray pair-distribution function analysis for SrRu⁢O3,CaRu⁢O3, and one intermediate composition show them to display monoclinic symmetry at the local level; when averaged over different domain orientations this yields orthorhombic symmetry in the long range, and no long-range or local phase transitions are observed between 80 and 300 K for materials with intermediate compositions. High-resolution transmission electron microscopy shows that the Sr/Ca distribution is random at the nanoscale. We plot magnetic characteristics such as the ferromagnetic 𝑇⁢c, Curie-Weiss theta, effective moment, and ambient temperature susceptibility vs the octahedral tilt and unit-cell volume.