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 T_Cᵇᵘˡᵏ 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 T_Cᵇᵘˡᵏ and, as temperature is varied, the surface magnetization is found to depart linearly from the nonzero value it assumes at T_Cᵇᵘˡᵏ, with critical exponents x₊=1.00±{}0.03 (T>T_Cᵇᵘˡᵏ) and x_-=1.00 ±{}0.01 (TT_Cᵇᵘˡᵏ). These findings are discussed in the light of recent theoretical studies.