Effect of quenching on magnetic properties of polycrystalline Pr0.5Sr0.5MnO3 perovskite manganite

The effect of quenching on the magnetic properties of polycrystalline Pr0.5 Sr0.5MnO3 has been investigated. Quenching samples from 1400 degreesC to ro om temperature in water (sample I) or in air (sample II) allows them to cry stallize in two different systems and to exhibit different magnetic behavio r at low temperature. Powder X-ray diffraction patterns for samples I and I I could be indexed, respectively, in the rhombohedral perovskite structure with R (3) over barc space group and an orthorhombic one with Imma space gr oup. Magnetization measurements show that bath samples exhibit a paramagnet ic-ferromagnetic transition at 280 K (sample I) and 265 K (sample II). At l ow temperature, sample I presents a ferromagnetic canted spin state or a mi xture of ferromagnetic and canted phases, while sample II behaves as an ant iferromagnet below 160 K. (C) 2001 Elsevier Science B.V. All rights reserve d.