Eur. Phys. J. B 12, 331-334 (1999)
https://doi.org/10.1007/s100510051012

The Rhodes-Wohlfarth parameter as assessment of the displacive degree in ferroelectrics: The case of the φ⁴ model

¹ Depto. de Física de la Materia Condensada, Facultad de Ciencias, Universidad del Pais Vasco, Apdo 644, 48080 Bilbao, Spain
² Físika Aplikatua II Saila, Zientzi Fakultatea, Euskal Herriko Unibertsitatea, P.K. 644, 48080 Bilbo, Spain
³ Depto. de Física Fundamental, Universidad de la Laguna, Tenerife, Spain

Corresponding author: ^a wmppemam@lg.ehu.es

Received: 23 December 1998
Revised: 4 May 1999
Published online: 15 December 1999

Abstract

The Rhodes-Wohlfarth parameter extended to ferroelectrics by Tokunaga [J. Phys. Soc. Jap. 57, 4275 (1988)] is here analyzed within the model. It is shown that it can be directly related with the displacive degree of the transition as described by the ratio , between the non-local coupling, C, driving the transition and the depth of the energy well, E₀, associated with the distorted structure. However, the Rhodes-Wohlfarth parameter becomes asymptotically constant as decreases, i.e. for systems closer to the order disorder limit. Under this viewpoint, the very limited range of values observed for this experimental parameter is explained and is shown that, in general, it can only assess quantitatively the character of the transition in rather displacive cases. The argument can be generalized to more complex systems, and when applied to well known materials, a rough estimation of the displacive degree and the relevant microscopic energetic parameters in rather displacive ferroelectrics is possible.