Birefringence investigations of the Sn₂P₂(Se_xS_1−x)₆uniaxial ferroelectrics behaviour near the lifshitz point

Lattice dynamics and phase transitions in Sn_{2}P_{2}S(Se)_{6} ferroelectric crystals

“…The experimental data for Sn 2 P 2 S 6 concerning the anomalous behavior of dielectric susceptibility [25], sound velocities [26], birefringence [27], diffuse scattering of X-rays [28] are generally well described in accordance with the predictions in [24] for the dipole Lifshitz point which is close to the tricritical point: the merging of these points preconditions a new universality class -the dipole tricritical Lifshitz point. However, the renormalization group description [24] is based on the uniaxial ferroelectric model of orthorhombic syngony -for this case the modulation wave in its IC phase is exactly transversal.…”

Complete spectrum of long-wavelength phonon modes inSn2P2S6Hlinka1, Gregora2, Vorlı́ček3 2002Phys. Rev. B351230View full textAdd to dashboardCite

“…The crystal of Sn 2 P 2 S 6 is a well-known uniaxial semiconductor ferroelectric with Curie point near 337 K. 1,2 Its properties have been recently reinvestigated by a number of methods, including inelastic neutron scattering, 3 x-ray photoemission, 4 birefringence, 5 and Mössbauer 6 and ultrasonic 7 spectroscopies, as well as by dielelectric, 8 acoustoelectric, 9 and electro-optic 10 measurements. Several promising applications of this material have been found, too.…”

The second order phase transition in Sn_2P_2S_6 crystals: anharmonic oscillator model

“…The reason is that part of the domain cannot be switched by external field. The temperature dependence of the order parameter can be more accurately determined from optical experiments, particularly, from birefringence studies [16]. So, we use these data in our calculations (see figure 1).…”

“…This curve is also present in figure 3. The left side of equation (15) can be expressed in the terms of these ratios using (16). The ratio ω 2 (0)/ω 2 (300) in the right side of equation (15) can be calculated directly using the experimental values of corresponding frequencies.…”