Showing papers by "Nagoya Institute of Technology published in 1969"

Phenomenological Theory of Antiferroelectric Transition. I. Second-Order Transition

Abstract: Kittel's free energy expression as normalized to involve only dimensionless variables, and manipulated to explain behaviors of second-order linear antiferroelectrics. It is a function of polar and antipolar variables, each of which are proportional to sum and difference of polarizations of two sublattices respectively, and it contains dimensionless temperature and external field as parameters. Free energy maps as functions of the two variables were computed at various values of two parameters. They visualize stability of states and how induced transition occurs under the external field. Stabilities of states were examined analytically, and restrictions on the two parameters for stability were obtained. Below the transition point antiferroelectric state is always more stable than polar state. Under external field, the well-known double hysteresis loop was explained satisfactorily considering stability of the state on two branches of polarization vs. field. Critical field for induced transition was also cal...

Thermostatistical Investigation of Magnetic and Thermal Properties of Cobalt Dichalcogenide Compound Co(SxSe1-x)2 with Pyrite Structure

Abstract: A statistical-mechanical calculation on the system of spins of quantum number one half which constitute a face-centred cubic lattice and couple not only with the nearest-neighbour spins but also with the second-neighbour spins due to the exchange interactions is carried out with the use of the inverse temperature expansion. By the application of this calculation, the magnetic and thermal properties of cobalt dichalcogenide compound Co(S x Se 1- x ) 2 of various values of the fraction x with pyrite structure is discussed, assuming that the antiferromagnetic exchange coupling between a pair of second-neighbour spins gets stronger with decreasing of the fraction x . The correspondence between the theory and experiment is quite well in all respects. The appearance of a certain metamagnetic transition is predicted in the compound of an intermediate x value which is not ferromagnetic although no ample measurement of the magnetization in variable magnetic field at various temperatures has been carried out yet en...