Analysis of experimental specific heat data near the critical temperature. II. Analysis of DAG, MnCl2.4H2O, GdVO4and GdAlO3

For pt.I see ibid., vol.8, p.4037 (1975). The method of data analysis developed previously is applied to the analysis of real specific heat data for three rare earth salts, DAG, GdVO 4 and GdAlO 3 , and MnCl 2 .4H 2 O. All these compounds order antiferromagnetically at liquid helium temperature. The data are fitted to C/R=B+A(T/T N -1) - alpha for T>T N , and it is found that alpha =0.13+or-0.04 for all four compounds, A approximately=-B=1.2+or-0.5 for the three rare earth salts and A approximately=-B=2.0+or-0.7 for MnCl 2 .4H 2 O. This is in surprisingly good agreement with theoretical Ising model predictions of alpha = 1 / 8 , A approximately=1.1 and B approximately=-1.24, despite the fact that only DAG and MnCl 2 .4H 2 O have Ising-like anisotropy. For all four compounds the Neel temperature was found to lie between 1 / 2 and 1 1 / 2 mK above the specific heat peak.