Thickness-dependent coercivity of ultrathin Co films grown onCu(111)

Abstract

By using the magneto-optic Kerr effect (MOKE) we have investigatedthe coercivity of ultrathin epitaxial Co films grown by molecularbeam epitaxy with the aid of Pb as the surfactant on Cu(111). Wefind two different regimes: below ~6 ML (ML≡monolayer), the coercivefield Hc increases continuously, whereas for thicker layersit falls at a rate that is inversely proportional to the filmthickness. While this latter behaviour is typical for bulk systems,we show that the initial one is an effect of reduced dimensionality,reflecting the variation of the Curie temperature of the magneticfilms in the same thickness range. This phenomenon could haveimportant implications for atomic-scale engineering of magneticmaterials.