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Magnetic Properties and Mössbauer Investigations of La 0.67 Sr 0.33 Fe x Mn 1−x O 3 ( x = 0 and 0.5) Perovskites

Research paper by Itegbeyogene P. Ezekiel, Thomas Moyo

Indexed on: 13 Oct '18Published on: 02 Oct '18Published in: Journal of Superconductivity and Novel Magnetism



Abstract

We report magnetic phase separation in pure La0.67Sr0.33Fe x Mn1−x O3 (x = 0 and 0.5) ceramic samples. Rhombohedral crystal structures obtained with R3C space group show no significant changes in the lattice structures due to the close values of ionic radii of Fe3+ and Mn3+ ions. However, significant changes occur in the magnetic properties due to competing ferromagnetic (FM) and antiferromagnetic (AFM) interactions because of the presence of Fe3+ substitution. The FM double exchange interactions (DE) (Mn3+–O–Mn4+) appears suppressed by AFM superexchange interactions (Fe3+–O–Mn4+, Fe3+–O–Fe3+, Mn4+–O–Mn4+). The saturation magnetization for x = 0 has the highest value of approximately 80 emu/g at 2 K, which dropped significantly to approximately 5 emu/g at 2 K for the x = 0.5 sample. The coercivity (H c) for x = 0.5 increased from 161 Oe at 300 K to 786 Oe at 2 K compared with that of x = 0 which varied from 110 to 150 Oe. A value of H c(0) = 1.5 ± 0.04 kOe was extrapolated from the model fit to the temperature dependence of H c. The temperature-dependent 57Fe Mössbauer spectroscopy measurements show the presence of Fe in two different environments that have an AFM Fe3+–O–Mn4+ and Fe3+/2+–O–Fe3+/2+ coordination. The unequal fraction population of Fe ions at both AFM environments seems to increase the exchange bias effect.