ISING-TYPE BEHAVIOUR OF CRITICAL PROPERTIES IN WEAK FERROELECTRIC Li_{2}Ge_{7}O_{15}

Abstract

The dielectric constant ε and electron spin resonance spectra of Mn 2+ions have been studied in the range of the ferroelectric phase transition in Li 2 Ge 7 O 15 single crystals. Analysis of the experimental data permits one to estimate the critical exponents of dielectric susceptibility γ ∼ = 1.25, order parameter β ∼ = 0.32 and correlation length ν ∼ = 0.63. The values of the critical exponents determined in a fairly broad temperature interval around T c , are consistent with the theoretical predictions of the Ising model with a one-component non-polar ordering coordinate.