Abstract
We have determined the field-scaling parameters of the magnetic specific heat of the three-dimensional (3D) Ising antiferromagnet near , in an induced staggered magnetic field . The measurements were made in external fields 0≤H≤1.92 T using a capacitance technique. The H=0 results yield values of α=0.109(6) and /=0.538(6) for the critical exponent and amplitude ratio, respectively, in excellent agreement with renormalization-group (RG) predictions for the 3D Ising model. From the angular dependence and magnitude of the rounding of the phase transition with H, we find , as was earlier predicted by Alben et al. The data for H>0 were analyzed using the so-called linear parametric model (LPM) for the equation of state, which has been shown to be correct to order in the RG theory by Wallace, but only for Ising systems. An excellent fit of the data to the LPM was obtained. From the field scaling of the data, a value of δ=4.94(13) is obtained for the critical isotherm exponent, in good agreement with the RG result δ=4.82(2). This is the first time δ has been experimentally determined for an antiferromagnet. For the optimum orientation of the magnetic field with respect to the crystalline axes, we obtained mT at H=1.92 T. A similar study in shows that a maximum staggered field of only 0.024(13) mT is induced in this system by the application of the same uniform field.
- Received 15 May 1989
DOI:https://doi.org/10.1103/PhysRevB.40.7124
©1989 American Physical Society