Seminar: Role of pressure on Critical Behavior of some Perovskite Manganites

Professor S. Arumugam, the director of the Centre for High Pressure Research at Bharathidasan University in India, is going to give a seminar at 10am on June 12, 2015 at East 4-242 in ZiJinGang Campus. Below is the abstract of the seminar.

Role of pressure on Critical Behavior of some Perovskite Manganites

Prof. S. Arumugam

Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli 620 024, India

Abstract
The high-pressure technique has been recognized as one of the powerful tools to investigate the physical properties of solids because pressure can vary physical parameters cleanly, not introducing disorder. High pressure, which effectively increases the electron transfer interaction or the one electron band-width, is a powerful tool for investigation of the electronic and magnetic properties of manganites. In this lecture, few results on critical behavior of cubic perovskites under pressure and magnetic field will be discussed. Hydrostatic pressure dependence of the order of phase transition in (Sm0.7Nd0.3)0.52Sr0.48MnO3, La0.4Bi0.3Sr0.3MnO3 and Pr0.6Ca0.4Mn0.96B0.04O3 (B = Co and Cr) systems were analyzed. At ambient pressure, these systems undergo a first-order paramagnetic insulator to ferromagnetic-metallic phase transition. The application of pressure on magnetization of (Sm0.7Nd0.3)0.52Sr0.48MnO3 and La0.4Bi0.3Sr0.3MnO3 systems suppress the first-order paramagnetic to ferromagnetic, and leads the second-order one under 1.21 and 0.91 GPa. Similarly, first-second order crossover takes place, are 2.02 and 2.40 GPa for Co and Cr doped samples respectively. In order to understand the nature of ferromagnetism in second order transition, it is essential to determine the critical values, and the assigning them for existing theoretical models such as mean-field, tricritical, Heisenberg and 3D Heisenberg etc., Here, the estimated values for (Sm0.7Nd0.3)0.52Sr0.48MnO3 and Pr0.6Ca0.4Mn0.96Co0.04O3 are close to the 3D Heisenberg model for the Co doped sample suggesting short-range FM interaction. On the other hand, the estimated values for La0.4Bi0.3Sr0.3MnO3 and Pr0.6Ca0.4Mn0.96Cr0.04O3 are close to the 3D Heisenberg model for the Co doped sample suggesting long-range interaction.