Pressure Induced Critical Behavior of Ferromagnetic Phase Transition in Sm-Nd-Sr Manganites

We report on the hydrostatic pressure dependence of the order of ferromagnetic (FM) to paramagnetic (PM) phase transition in a (Sm0.7Nd0.3)(0.52)Sr0.48MnO3 single crystal. At ambient pressure, the system undergoes a first-order FM-PM phase transition at 146 K. The application of pressure increases the T-C, suppresses the hysteresis width, and thus makes the transition second order. We have analyzed the critical behavior associated with the second-order FM-PM transition in the presence of an external pressure (12.1 kbar) and obtained the critical exponents beta = 0.358, gamma = 1.297, and delta = 4.536, which are close to those predicted for the three-dimensional Heisenberg system. Using these values of beta, gamma, and T-C (similar to 176 K), one can scale the magnetization data below and above T-C following a single equation of state.