Effect of growth temperature on Curie temperature of magnetic ultrathin films Co/Cu(100)

The magnetic and structural properties were investigated for the 2 ML Co/Cu(100) films grown at various temperatures from 125 to 350 K. By precisely controlling the film thickness, the influence of thickness on Curie temperature (T_C) due to the finite size effect can be excluded. The Curie temperature of the 2 ML Co keeps almost invariant for the growth temperature (T_g) below 250 K, and drops drastically at T_g, higher than 275 K. For T_g = 340 K, T_C dropped to 170 K which is only about half of 325 K for T_g = 125 K. Accompanied with the increase of T_C for the films grown at lower temperatures, the remanent Kerr signal as well as coercivity were enhanced. According to a simple theoretical estimation, the change of T_C due to the variation of the magnetization and anisotropy was found to be consistent with the experimental results. The enhancement in T_C or magnetization and anisotropy with various T_g should be traced back to the presence of island growth in the films grown at lower temperatures.