INVESTIGATION OF THE DYNAMIC PROPERTIES OF PHASE TRANSITIONS OF ORDERED MAGNETIC STATES

摘要

This Final Report consists of two parts, along the lines of the two dis¬tinct research topics included in the contract. In Part 1, we report our research on the properties of magnetic phase transitions. We have made a survey of the mate¬rials which undergo magnetic phase transition, suggested some experiments which should be useful in their study, and performed several of these experiments on the spin flop transition in antiferromagnetic CuCl2 SH2O. The magnetization of a mate¬rial undergoing a magnetic phase transition is a highly non-linear function of the magnitude and orientation of applied magnetic field;therefore the differential sus¬ceptibility is large. By measuring the susceptibility as a function of frequency, we have determined that the relaxation time for the spin flop transition in CuCl2.2H2O is 7 x 10-8 seconds. The component of magnetization perpendicular to the applied magnetic field, as well ás the parallel component, should be highly non¬linear. We have measured the components of the susceptibility tensor relating to the perpendicular magnetization and obtained data in approximate agreement with a theoretical analysis based on the molecular field approximation. Some discrepancies were observed, and these are believed to be caused by spin canting and crystal im¬perfections. In Part 2, we report our research on the optical properties of tran¬sition metal ions, in crystalline solids.