Department of Physics, Engineering Physics & Astronomy

Department of Physics, Engineering Physics & Astronomy
Department of Physics, Engineering Physics & Astronomy

Crossover from pure to random field critical properties in an Ising ferroelectric system

Prof. Don Taylor
Department of Physics, Queen's University

Wednesday, February 16, 2005
10:30 AM @ Stirling 501

Abstract:

The effects of random static local fields on critical properties at a phase transition have been studied extensively for many years, particularly for Ising model systems. After a period of uncertainty and controversy, the predictions of theory have become generally accepted. However experimental research on such systems has proven to be difficult and progress has been slow. After a review of phase transitions and random field effects I will describe recent experiments on a new ferroelectric realization of a random field system, KH2(As,P)O4. The precise susceptibility measurements available in a ferroelectric system have made it possible to observe a clear crossover from pure to random-field critical behaviour as a function of temperature. The results are consistent with theory that predicts that random fields essentially reduce the dimensionality of the system.