Critical scattering from erbium

Neutron scattering techniques have been used to measure the nature of the phase transition in erbium at TN=87 K from paramagnetism to an incommensurate longitudinally ordered phase with q=0.283 along c at TN. A high-purity crystal showed normal critical scattering in the paramagnetic state with a different correlation length in the basal plane and along c. It is found that γ=0.96±0.06 and both correlation lengths diverge with the same critical exponent ν=0.49±0.02 for a range of reduced temperature from 0.0015 to 0.07. In the ordered state, power-law behavior was observed with β=0.48±0.02 for reduced temperatures between 0.005 and 0.04. Below TN the intensity of the third harmonic varied as the cube of the reduced temperature. All these observations correspond to mean-field behavior.