Critical exponents and amplitude ratio by direct measurement of dR/dT in erbium.

Abstract

High-precision data of the electrical-resistance temperature derivative dR/dT along the c axis of a single crystal of erbium have been obtained using a direct measurement method. Numerical analysis of the dR/dT data for this helical antiferromagnet system provides a quantitative verification of the theory of scattering of electrons by spin fluctuations in the vicinity of the N\'eel temperature ${\mathit{T}}_{\mathit{N}}$ in a single crystal of Er. In addition, the accuracy of the present results enabled us to check the agreement between our results and the theoretical predictions of critical exponents and amplitude ratio obtained by renormalization-group (\ensuremath{\epsilon}-expansion and field-theoretical) methods. The results can be well described using the mean-field theory far from the critical region and above ${\mathit{T}}_{\mathit{N}}$. However, below ${\mathit{T}}_{\mathit{N}}$ and far from the transition region, an exponential law is suggested.