Surface magnetization of Gd at the bulk Curie temperature

Electron-capture spectroscopy is used to study the long-ranged surface ferromagnetic order of Gd in the neighborhood of the bulk Curie temperature ${\mathrm{T}}_{\mathrm{C}{}^{\mathrm{bulk}}}$ at which, unlike bulk ferromagnetic order, it does not vanish. The surface magnetization, together with its first temperature derivative, is found to be a continuous function of temperature at ${\mathrm{T}}_{\mathrm{C}{}^{\mathrm{bulk}}}$ and, as temperature is varied, the surface magnetization is found to depart linearly from the nonzero value it assumes at ${\mathrm{T}}_{\mathrm{C}{}^{\mathrm{bulk}}}$, with critical exponents ${\mathrm{x}}_{+}$=1.00±0.03 (T>${\mathrm{T}}_{\mathrm{C}{}^{\mathrm{bulk}}}$) and ${\mathrm{x}}_{\mathrm{-}}$=1.00 ±0.01 (T<${\mathrm{T}}_{\mathrm{C}{}^{\mathrm{bulk}}}$). These findings are discussed in the light of recent theoretical studies.