The effect of pressure and magnetic field on the O-R structural phase transition in La1-xSrxMnO3 single crystals:: the transition heat

We study the effect of,pressure and a magnetic field on the temperature T-S of the structural transition from orthorhombic to rhombohedral phase in La1- xSrxMnO3 single crystals. The temperature dependence of the phase volumes and the jumps in saturation magnetization (x = 0.20 and 0.175) or magnetic susceptibility in paramagnetic state (x = 0.15) have been measured and then the transition heats have been determined. In all crystals, the transition heat is very small (< 0.6 kJ/mol). For given x, the heat derived from the T-S-H curve is less than that derived from the T-S-P curve, which is likely to indicate internal stresses in the crystals. (c) 2005 Elsevier B.V. All rights reserved.