Structure, microstructure and magnetic properties of Sr1−xCaxCrO3 (0⩽x⩽1)

The effect of the calcium concentration on the structural, microstructural and magnetic properties of Sr(1−x)CaxCrO3 with 0⩽x⩽1 has been studied. The compounds were prepared using high pressure and high temperature synthesis. X-ray diffraction shows that the samples evolve from the cubic Pm-3m space group for x=0–0.2 to tetragonal I4/mcm for x=0.4–0.5, then to the orthorhombic Pbnm space group for x=0.6, 0.8 and 1.0. Electron diffraction and high-resolution transmission electron microscopy confirmed the respective cells for the end compositions: ap×ap×ap (Pm-3m) for SrCrO3; and the 2ap×2ap×2ap (Pbnm) for CaCrO3. For intermediate compositions some extra spots appear in the electron diffraction patterns while the electron micrographs indicate the presence of microdomains. Magnetic measurements show Curie–Weiss behaviour at high temperature for all the samples. A sharp antiferromagnetic (AFM) transition at about 91.5 K appears for x=0.8–1 together with a weak ferromagnetic ordering below TN.

HRTEM image of a crystal of Sr0.5Ca0.5CrO3 showing a random distribution of 2ap≈7.6 Å all along the crystal that lacks long range order. Inset shows the FFT of the area of the image and of a tenth of that area showing the influence of the coherence length.Figure optionsDownload as PowerPoint slide