Naslov
Landau Model for Commensurate-Commensurate Phase Transitions in Uniaxial Improper Ferroelectric Crystals

Autori
Latković, Mladen ; Bjeliš, Aleksa ; Dananić, Vladimir

Izvornik
Journal of Physics - Condensed Matter (0953-8984) 12 (2000), 19; L293-L302

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Landau model; A_2BX_4 compounds; phase transitions; improper ferroelectrics

Sažetak
We propose the Landau model for lock-in phase transitions in uniaxially modulated improper ferroelectric incommensurate-commensurate systems of class I. It includes Umklapp terms of third and fourth order and secondary order parameter representing the local polarization. The corresponding phase diagram has the structure of harmless staircase, with the allowed wave numbers obeying the Farey tree algorithm. Among the stable commensurate phases only those with periods equal to odd number of lattice constants have finite macroscopic polarizations. These results are in excellent agreement with experimental findings in some A_2BX_4 compounds.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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