Modeling of polar clusters in disordered perovskites: The S-K model with tunneling

• Autor(a) principal: Almeida, B. G.
• Data de Publicação: 2000
• Outros Autores: Lacerda-Aroso, M. T., Ribeiro, J. L., Chaves, M. R., Almeida, A.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: https://hdl.handle.net/1822/85685
• topic: Solid-solid transitions; Domains; glass phase; ferroelectricity; Ciências Naturais::Ciências Físicas; Science & Technology

The polar clusters generated by random non-central impurities in quantum paraelectrics determine to a great extent the complex dielectric behaviour observed in systems like SCT, KTN or KTL. The competition between a quantum paraelectric phase and an impurity-driven ferroelectric or glass phase depends on the concentration and on the nature of the interaction between clusters. This work presents a simple model in which each cluster is represented by a quantum two level system involving an effective Ising dipolar moment and a tunneling energy A. The interactions between clusters are taken into account by following the guide-lines of the Sherrington-Kirkpatrick model for spin glasses. General expressions for the polarization (P) and the Edwards-Anderson order parameter (q) are given and the phase diagram involving temperature, the normalized mean interaction energy J0/J and tunneling energy A/J0 is built.