Study of reduced dimensionality effects in thin magnetic films

The growth, structure, magnetic properties and their inter-relationship of Ni and Ni alloy ultrathin films were studied using in situ surface magneto-optic Kerr effect and conventional ultrahigh vacuum techniques.; Layer-by-layer growth is observed in the films grown on Cu(100) and (110) substrates. During the film deposition, the oscillatory behavior of the relaxation for the surface layer atoms is observed and explained by a simple model for the strain. A layer-by-layer growth of Ni films on a Cu(111) is achieved by using Mn as the surfactant which also changes the relaxation behavior of the surface layer atoms due to the involvement of Mn atoms at the growth front.; The growth and structure have a great impact on the magnetic anisotropy through the epitaxial strain in the films. By measuring the strains in the film and the crossover thickness for the in-plane to out-of-plane spin reorientation transition, we extracted the surface anisotropy for various films which shows a linear relationship with the alloy composition and is dependent on the film crystalline orientation. This result suggests a direct relationship of the magnetic surface anisotropy with the magnetostriction effect. The unusual spin reorientation behavior in Ni films is influenced by the alloying and film crystalline orientation. This behavior is observed for the first time in Ni(111)/Cu films due to the use of Mn surfactant, which improves the film quality.; The thickness dependent crossover of lattice and spin dimensionality were also observed. The lattice-dimensional crossover is film orientation and alloy composition dependent. This crossover thickness is related to the dimensions of the appropriate Fermi surface, which we interpret in term of a simple quantum-well-states model. The crossover of spin-dimensionality is driven by the magnetic anisotropy.; A simple spin interaction model is developed to account for the discrepancy of the experimental result and the finite-size scaling law. This model shows that the thickness dependent critical temperature crossover from power law to linear behavior as the thickness approaches the critical scaling length parameter No, which we believe reflects the strength of the coupling of the critical fluctuations.