Examination of Logarithmic Corrections to the Classical Landau-Type Theory by the Dilatometric Study of TGS

Precise dilatometric measurements of TGS revealed an existence of a distinct departure in the coefficients β 2 of thermal expansion from the mean field theory (MFT). In the reduced temperature range, -3.17<log 10 - t <-1.87, the data of β 2 fit well to the formulas given by a connection between the Larkin-Khmel'nitskii theory (LKT) and the Pippard relations. The fitted formulas explain satisfactorily also the behavior above T c , except for the close vicinity of T c considered as the region of `rounding'. In the wide range, 80 K to 321 K, a good agreement with the MFT is obtained by taking suitable parameters. The jump Δ β 2 derived from the MFT-fit is comparable with the corresponding value in the LKT. A comparison between the results of TGS and dipolar Ising ferromagnet LiTbF 4 was made.