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Sr1 − x Ca x Mn0.5Ti0.5O3 (x = 0.25, 0.5 and 0.75) polycrystalline samples were synthesized by conventional solid-state reaction. Magnetic characterizations of Sr1 − x Ca x Mn0.5Ti0.5O3 revealed signature of antiferromagnetic ordering at temperatures (T N) ~19, 25 and 29.5 K for x = 0.25, x = 0.5 and for x = 0.75, respectively. Sr1 − x Ca x Mn0.5Ti0.5O3 (x = 0.75) exhibits field-induced antiferromagnetic to ferromagnetic transition at ~30 K with applied magnetic field of 4 and 5 T. Magnetocaloric change (ΔS M) increases from 3.5 to 19 J/kg K by increasing calcium concentration in the A-site. Those ΔS M values are relatively very high in these classes of antiferromagnetic perovskite systems and equal to the magnetisation values of the ferromagnetic perovskite manganites. This is the first report for the Sr1 − x Ca x Mn0.5Ti0.5O3 (x = 0.75) having large magnetic entropy changes induced by the low magnetic field.

The oxygen-deficient strontium iron oxide SrFeO3−δ (SFO) exhibits richness in the phase diagram over a broad range of temperatures and for other external parameters. Room-temperature X-ray diffraction and Raman spectrum reveals that the structure of synthesized SFO system consists of two mixed phases, i.e., major orthorhombic and minor tetragonal phases. The low-temperature Raman and vibrating sample magnetometer measurements indicated a structural transition below 253 K. The magnetic property of the synthesized SFO for various external magnetic field (up to 5 T) reveals possible variation in oxygen stoichiometry. Also, the application of external H increases Neel transition temperature (T N), suppresses the hysteresis width (W H), and thus weakens the first-order nature of the transition. Our analysis revealed the vanishing of hysteresis and the first-order antiferromagnetic transition becomes a crossover above a critical magnetic field H CR ≈ 5 T. Possible switching of magnetic ordering and oxidation state observed in same system enhances interest in related compounds which may be used in magnetic sensors and other magnetic switching devices.