Transition regions in the parameter space based on the transverse Ising model with a four-spin interactionB. H. Teng1, 2 and H. K. Sy2
1 School of Physical Electronics, University of Electronic Science and Technology of China - Chengdu 610054, PRC
2 Department of Physics, National University of Singapore Kent Ridge, Singapore 117542, Republic of Singapore
received 9 September 2005; accepted 28 September 2005
published online 21 October 2005
By taking into account the four-spin interaction in the transverse Ising model (TIM), the transition feature of the ferroelectric thin film is investigated within the framework of the Green's function technique. Various transition regions in the parameter space with respect to the ratios of the tunneling frequency and the four-spin interaction to the two-spin interaction are calculated by a higher-order decoupling approximation beyond the usual mean-field approximation. The results show that the transition regions are greatly different from the ones obtained within the framework of the mean-field approximation. It is suggested that the usual mean-field approximation exaggerates not only the second-order but also the first-order ferroelectric transition regions for a ferroelectric thin film.
77.80.Bh - Phase transitions and Curie point.
75.10.Hk - Classical spin models.
77.55.+f - Dielectric thin films.
© EDP Sciences 2005