The critical specific heat of terbium

Specific heat measurements have been carried out on a high-purity single crystal of terbium of mass 3.734 g between temperatures of 200 and 400K. The data around the Neel temperature T N , have been analysed in terms of the equation C +or- =(A +or- / alpha +or- ) mod t mod - alpha +or- (1+E +or- mod t mod x+or- )+B +or- +D +or- t where t=(T-T N +or- )/T N +or- . The parameters obtained from our best fit are alpha + = alpha = - 0.20+or-0.03, A + /A - =0.58+or-0.34, B + =B - =21.68+or-13.93 J mol -1 K -1 , E + /E - =-2.06+or-4.12, D + =D - =4.99 J mol -1 K -1 and T N + =T N - =229.9503+or-0.0035K. This fit is valid in the critical regions -3.4<lg mod t mod <-1.5 below T N and -3.9<lg mod t mod <-2.2 above T N . The authors find that the relation T N + =T N - is obeyed and that the scaling law alpha + = alpha - is valid in this region. In order for the condition B + =B - , predicted by theory, to be satisfied they have found it necessary to include the confluent singular term in E in the fit. The value of alpha (=+0.20) that the authors obtain is not close to the predictions of renormalisation group theory for magnetically collinear systems with short-range interactions. A cross-over from the critical region to a region with different behaviour is observed at lg mod t mod =-2.2 above T N , but not below it.