Neutron diffraction, NMR and magneto-transport properties in the Pr0.6Sr0.4MnO3 perovskite manganite

A Pr0.6Sr0.4MnO3 powder was synthesized by the solid state reaction method at 1400degreesC. Magnetic measurements show that our sample exhibits a paramagnetic-ferromagnetic transition with decreasing temperature. The paramagnetic to ferromagnetic transition is followed by a decrease of the magnetization below 100 K. The Curie temperature T-C is found to be 310 K. Electrical studies show a semiconductor-metallic transition at T-p = 260 K. Our sample displays a magnetoresistance effect in 8 T of about 45% below 250 K. Neutron diffraction studies show that our sample crystallizes in the orthorhrombic system with Pnma space group at room temperature and at 200 K. However, at 10 K, we observe the coexistence of two phases: an orthorhombic phase with Pinna space group (27%) and a monoclinic one with 12/a space group (73%). Mn-55 NMR measurements at 4.2 confirm the metallic behavior at low temperature. The observed frequency of 380 MHz is close to the calculated frequency of 378 MHz, which confirms the average value of Mn4+ and Mn3+ resonance frequencies. (C) 2002 Elsevier Science BY. All rights reserved.