Critical exponents and amplitude ratios from electrical resistivity measurements of dysprosium

Resistive anomalies in helical antiferromagnets are shown to reflect the temperature dependence of the specific heat sufficiently close to the Néel temperature. The temperature dependence of superzone energy gaps does not enter. Numerical analysis of electrical-resistance data for a helical antiferromagnet, dysprosium, provides quantitative support for theoretical estimates of critical exponents and amplitude ratios obtained by renormalization-group $\epsilon$ expansions and by field-theoretical methods and suggests that dysprosium is described by a model whose order parameter has $n=4\mathrm{}$ degrees of freedom.