Phase transitions in Ising plates of equal area and different thicknesses have been studied by the Monte Carlo approach. The evolution of the critical temperature and of the effective critical exponents with the thickness of the lattice has been numerically determined. The thickness dependence of the maximum value of the effective critical exponents is well described by an exponential decay towards the respective three-dimensional value.
Relaxational behavior of ferroelectric telluric acid ammonium phosphate crystals were investigated in the range 20 Hz to 1 MHz by means of low field measurements of ε' and tan δ in the vicinity of ferroelectric phase transitions at a number of frequencies. Results are compared with those for triglycine selenate, a much "softer" ferroelectric material. The measuring field and frequency dependence of the effective potential barrier height for domain wall motion are compared in both crystals.
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