Analysis Of The Specific Heat For The Transitions Of The Phases Ⅰ-Ⅱ-Ⅲ- Ⅳ In (n(ch_3)_4)_2cucl_4 Crystal

摘要

The temperature dependence of the specific heat C_p is analyzed here using the experimental data according to a power-law formula with the critical exponent α for the transitions of commensurate (Ⅰ), incommensurate (Ⅱ) and the ferroelastic (Ⅲ and Ⅳ) phases in (N(CH_3)_4)_2CuCl_4 crystal. From our analysis, we extract the value of α ≈ 0 above and below T_c for the successive phase transitions of Ⅰ-Ⅱ-Ⅲ, which is expected from the mean field theory (α =0 discontinuity), XY model (α =0 log) and the two dimensional Ising model (α =0 log). This indicates that the transitions between commensurate and incommensurate phases and also between incommensurate and ferroelastic (Ⅲ) phases in TMATC-Cu are of a second order type.rnIt is indicated here that the transition between the ferroelastic phases Ⅲ and Ⅳ in TMATC-Cu should be further investigated using theoretical models.