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The Low‐Temperature Expansion of the Polarization of KDP‐Like Crystals
Author(s) -
Kapor D. V.
Publication year - 1976
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220740210
Subject(s) - anharmonicity , hamiltonian (control theory) , pauli exclusion principle , condensed matter physics , curie temperature , polarization (electrochemistry) , unitary state , physics , mathematical physics , ferroelectricity , quantum mechanics , ferromagnetism , mathematics , chemistry , dielectric , mathematical optimization , political science , law
The Hamiltonian of a KDP‐type ferroelectric is formulated in terms of Pauli‐operators. Canonical and unitary transformations are applied which bring the Hamiltonian into a form suitable for the Green's function method analysis. The whole theory is linear in the small parameter η = Ω/ I (0). The low‐temperature expansion for the polarization is calculated (using the exact Bose‐representation of Pauli‐operators in the first approximation) exibiting T 2 and T 3 anharmonic corrections. In the case of high temperatures, the Curie‐Weiss law is reproduced with a transition temperature lower than in the mean‐field approximation.