Magnetic Behavior of Thin Films of Nickel and Gadolinium Near the Curie Point

Magnetization measurements have been made on thin films of nickel and gadolinium near the Curie point using a torque technique. The films were prepared by evaporation in pressures of 10−7 and 10−8 Torr. Most of the measurements were made with a torsion magnetometer and the others with an automatic torquemeter system. The relative magnetization σ near but below Tc is described by σ = D(1−τ)f, where τ = T/Tc. The value of f is obtained by using the procedure of Callen and Callen. Plots of σ(1−f)/fdσ/dτ for nickel films were flat for f = ½ for temperatures 0.90<τ<0.95 and peaks for f = ⅓ are observed at lower temperatures. Gd films gave f = 0.6 for temperatures 0.8<τ<0.9 and f = ½ for τ>0.9. The ½-power behavior is in agreement with molecular-field theory and the Landau theory for second-order transitions.