We measure the magnetic susceptibility of ultrathin Co films with an in-plane uniaxial magnetic anisotropy grown on a vicinal Cu substrate. Above the Curie temperature the influence of the magnetic anisotropy can be investigated by means of the parallel and transverse susceptibilities along the easy and hard axes. By comparison with a theoretical analysis of the susceptibilities we determine the isotropic exchange interaction and the magnetic anisotropy. These calculations are performed in the framework of a Heisenberg model by means of a many-body Green's function method, since collective magnetic excitations are very important in two-dimensional magnets.

The ac susceptibility of ultrathin Co/Cu(100) films has been investigated in situ under ultrahigh vacuum conditions using the magneto-optical Kerr effect. A conventional Kerr effect setup was combined with an ac-field modulation technique to improve the experimental detection limit. A sensitivity in the range of 10−8 rad for the Kerr ellipticity has been achieved in the present study. The ac susceptibility χac of the investigated cobalt films is mainly characterized by a pronounced and sharp maximum as a function of the temperature T. This χac(T) dependency corresponds to the ferromagnetic-paramagnetic phase transition occurring at the Curie temperature Tc of the cobalt films, which is also confirmed by experimental observation of the hysteresis behavior. Besides the measurement of Curie temperatures, the experimental technique presented here allows the determination of magnetic properties for ultrathin films even in the paramagnetic regime far above Tc.

The in-plane magnetic anisotropy of ultra-thin Co films, epitaxially grown on Cu͑1 1 17͒, was determined in situ by means of the magneto-optic Kerr effect down to thicknesses as low as 2 monolayers. Uniaxial and biaxial anisotropy contributions were observed. At room temperature, the uniaxial component is dominant and the easy axis of magnetization is parallel to the step edges. Above 4 monolayers the magnetic anisotropy exhibits a thickness dependence which can be described by volume and interface contributions. For thinner films a pronounced deviation from that behavior is found. The anisotropy drops abruptly by one order of magnitude below 3 monolayers. Thickness dependent relaxations are proposed as driving forces for that behavior.

Reactive joining, i.e., utilization of an exothermal reaction to locally generate the heat required for soldering or brazing, represents an emerging technology for flexible and benign joining of heat-sensitive materials, e.g., for microelectromechanical systems (MEMS) applications. However, for successful reactive joining, precise control of heat production and heat distribution is mandatory in order to avoid damaging of the components during the process. For the exemplary case of borosilicate glass, the reactive joining process for a both thermally and mechanically sensitive material is developed. Employing various nondestructive and destructive testing methods, typical problems which can occur upon reactive joining are identified, e.g., exposure of the joining zone to excessive temperatures, experience of thermal shock by the substrate due to sudden temperature increase, and generation of residual stresses in substrate and soldering zone. Utilizing the results of nondestructive and destructive testing, procedures for successful reactive joining of borosilicate glass, silicon and aluminum oxide are provided.

The temperature dependence of magnetic anisotropy in cobalt films grown on Cu(1 1 17) has been studied by means of the magneto-optic Kerr effect. An in-plane uniaxial anisotropy is found in the as-grown films. At elevated temperatures the films exhibit changes in anisotropy. At temperatures around 100'C a transition to nearly biaxial behavior is found which transforms again into uniaxial behavior at higher temperatures. Both transitions generate pronounced secondary maxima in the temperature-dependent susceptibility.One of today's most interesting topics in magnetism is ferromagnetism in thin 6lms and multilayers. Due to recent developments in the 6eld of epitaxy it becomes feasible to create materials in diferent forms of condensation, e. g., regarding their crystal structure and/or lattice constant. Such tailoring of material parameters allows one to investigate the dependence of magnetism on distinct, well-characterized properties of ferromagnets. This tendency in experimental magnetism is accompanied by strong activities in theory. 2 Some of the theoretically modeled systems may be realized as thin films now. Thus 6rst-principals calculations of magnetic properties may be compared with experimental findings giving a strong impetus to the understanding of magnetism in general.The dependence of magnetization on particular directions is known as magnetic anisotropy, which includes crystalline (i.e., symmetry), strain as well as shape effects. Hence, structure and morphology determine the anisotropy. Because the selection of a substrate and/or growth conditions ofFers the possibility of manipulating the magnetic behavior, a huge number of papers are dealing with anisotropy behavior of thin 6lms. The major point with the studies on magnetic anisotropies is to figure out which structural properties are predominantly reflected in the magnetic behavior.A strong impetus on activities in thin-film magnetism is related to the concept of surface anisotropies proposed by Neel.Neel pointed out the importance of the reduced symmetry at the surface of a ferromagnet. A new facet of Neel's approach of anisotropy has been proposed by Albrecht et al. recently. The reduced symmetry at surface steps caused additional twofold contributions to surface anisotropy. The authors could extrapolate such step anisotropy from their results.An elegant way to demonstrate the infIuence of steps on anisotropy is to study ferromagnetic 6lms grown on vicinal surfaces.Because of the step alignment and high step density on such surfaces, the influence of steps can be observed immediately as a strong twofold anisotropy. Recently it was demonstrated that first-principals calculations of electronic structure in fcc lattices are in good agreement with a Neel ansatz considering only nearest-neighbor interactions. Symmetry-based contributions to the anisotropy energy have been given. Based on this, a complete Neel ansatz including all energy contributions for a stepped ultrathin ferromagnet has been worked out. i The rigorous description shows twofold vo...