By comparing the surface and bulk magnetization of smooth, well-ordered Gd samples, we show that the surface has an ordinary transition, i.e., a common Curie temperature for surface and bulk. A quantitative statistical analysis of the temperature dependent magnetization is presented. Critical exponents for both surface, ${\beta }_S=0.83\mathrm{}\pm 0.04$, and bulk, ${\beta }_B=0.376\mathrm{}\pm 0.015$, are consistent with the semi-infinite three-dimensional Heisenberg model with homogeneous exchange.

• Received 23 May 2000

DOI:https://doi.org/10.1103/PhysRevLett.85.5202