Manipulation of the Curie temperature and the magnetic moments of ultrathin Ni and Co films by Cu-capping

Temperature-dependent studies are performed in situ on Ni/Cu(001) and Co/Cu(001) ultrathin films by AC-susceptibility and the element-specific X-ray magnetic circular dichroism. It is shown that the growth of a Cu capping layer reduces considerably the Curie temperature by about 30-40 K for Ni and 100 K for Co films. The effect is practically completed after the growth of the first few monolayers of the Cu capping layer. Further growth of Cu does not alter significantly the Curie temperature. We show that the Cu-capping results in a decrease of the magnetic moments and the relation of it to the reduced Curie temperatures is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.