Dielectric Critical Phenomena in RbHSO4

Measurements of the spontaneous polarization are made for RbHSO 4 . The results in the temperature range 0.1^° C < T 0 - T <100^° C are well explained by using the elastic Gibbs function of G 1 - G 10 =(1/2)χ P 2 +(1/4)ξ P 4 +(1/6)ζ P 6 and χ=(4π/ C )( T - T 0 ) with T 0 =-8° C , C =144°C, ξ=7.2×10 14 Jm 5 C -4 and ζ=4.2×10 19 Jm 9 C -6 . The value of δ defined by P ∝ E 1/δ at T 0 is obtained to be 3, the mean field value, in the range E ≥∼200 V/cm.