Magnetic and electrical properties by Ca2+ doping in SmCrO3 orthochromites

Abstract Spectroscopic (UV–vis and XPS) magnetic and electrical properties of the Ca2+ doped SmCrO3 system were phenomenologically investigated. The Cr3+, Cr5+, and Cr6+ species were identified by XPS spectroscopy in Sm1−xCaxCrO3 (0 ≤ x ≤ 0.20). Rietveld analyses of the X-ray diffraction data reveal a smooth decrease in the cel`l parameters assigned to the Cr6+ formation as a function of the Ca2+ content. Diffuse reflectance spectroscopy showed that the wider optical bandgap of the system corresponds to a charge transfer process, and it disappears for x ≥ 0.1, showing t2 g-eg electronic gaps. The electrical measurements were fitted in two temperature ranges; for low temperatures (85–150 K), a 3D variable-range hopping mechanism seems to prevail, while for the 150–300 K range, the electrical behavior is well represented by the small-polarons conduction mechanism. Magnetic properties of Sm1−xCaxCrO3 were highly sensitive to the Ca2+ content, and the TN values varied from 192 to 151 K for x = 0 and x = 0.20, respectively; TRS varied from 34 to 9 K for the same x values. Isothermal magnetization curves at 5 K suggest that, as a function of the Ca2+ content, the Γ4 ferromagnetic phase remains for x ≥ 0.04; while for x = 0 and x = 0.02, the Γ2 ferromagnetic phase is the only one observed.