Search

Brillouin light scattering has been exploited in situ to study spin waves in ultrathin Co/GaAs(0 0 1) films of different thickness in the range between 1 and 7 nm, i.e. both before and after the bcc–hcp phase transition. A marked evolution of the in-plane anisotropy has been observed in connection with the structural transformation. Measurements of the spin-wave frequency as a function of the in-plane direction and of the intensity of the applied magnetic field, as well as of the incidence angle of light, enabled us to determine the magnetic parameters of the films, including the in-plane anisotropy constants.

The structural and magnetic properties of FeTaN/FeSm/FeTaN multilayers, deposited by dc magnetron sputtering, have been investigated as function of the alloy layers thickness. Structural and morphological characterizations, accomplished by transmission electron microscopy, X-ray reflectivity and grazing-incidence X-ray diffraction, account for a well-defined layered structure of the multilayers with a limited interface roughness. The magnetization reversal process is examined experimentally using magneto-optical Kerr vector magnetometry by measuring the longitudinal and transverse hysteresis loops. It is found that, for soft layer thickness above 3.2 nm, the magnetization reversal occurs via the formation of a stable exchange-spring state in which the magnetic moments of the outermost soft layer gradually rotates away from the unswitched underlying hard layer.

The structural and magnetic properties of ultrathin Fe films, grown by e-beam evaporation on a Cu(1 0 0) single crystal, have been studied. The low-energy electron diffraction patterns account for a pseudomorphic growth of fcc-Fe(1 0 0) up to a thickness of a few nanometers, followed by a Pitsch transformation, consisting of bcc-Fe(1 1 0) domains. The magnetic properties of the films were investigated in situ by the combined use of surface magneto-optical Kerr effect and Brillouin light scattering. A ferromagnetic behaviour was detected for film thickness below about 1 nm and above 3 nm. A careful determination of the magnetic parameters and of the anisotropy constants of the ferromagnetic films was achieved by studying the dependence of the spin-wave frequency on the angle of incidence of light, on the intensity of the applied magnetic field and on its direction on the surface plane.

We report on the structural and magnetic properties of thin Fe films grown on the Cu(1 1 0) surface. In-plane grazing-incidence X-ray diffraction has been used to measure the lateral lattice spacing of the Fe films. Complementary information about the structure of the topmost layers has been obtained by means of Auger and photoelectron diffraction. The Fe film grows pseudomorphic with the substrate up to a thickness of about 0.8 nm. The diffraction feature of a new phase is observed at 1.6 nm, with a corresponding interplanar distance close to the bulk body centered cubic (bcc) Fe one, which is eventually recovered at higher thickness (6.4 nm). From comparison between X-ray diffraction and photoelectron diffraction, it is suggested that the bcc-like Fe grows on the (1 0 0) surface with its [1 1 0] axis oriented along the [0 0 1] substrate direction. The photoelectron diffraction data also indicate a strong faceting in the [1 1 0] substrate direction. This morphology is believed to contribute to the in-plane uniaxial magnetic anisotropy observed by Kerr effect and Brillouin light scattering from spin waves.

Ni/Cu multilayers were grown by RF sputtering. The crystal orientation, the thickness of the elemental layers and the interface quality were analysed by X-ray diffraction in the θ –2 θ configuration. Magnetic anisotropy was investigated by both a static and a dynamic technique, namely magneto–optical Kerr effect (MOKE) and Brillouin light scattering (BLS). Longitudinal MOKE loops accounted for the in-plane orientation of the magnetization, while polar loops were used to determine the out-of-plane anisotropy fields, showing the existence of a minor second-order contribution in addition to the first-order one. BLS was then exploited to detect thermal excited spin waves through inelastic scattering of light. The out-of-plane anisotropy fields evaluated by this high-frequency dynamic technique compare well with the first-order values obtained by analysis of polar MOKE hysteresis cycles.

Cu/Ni/Cu heterostructures have been in situ deposited on the 7×7 reconstructed Si(111) surface. A number of complementary techniques, such as in situ low-energy, medium-energy and Kikuchi electron diffraction and ex situ X-ray diffraction, were used in order to characterise the growth process and the structural properties of the films. It is found that the growth mode of metallic films is characterised by the presence of twinned islands induced by the 7×7 reconstruction of the Si(111) substrate. This work can stimulate further application of the metal–metal epitaxy on silicon to grow high quality ultrathin magnetic films to be integrated in microelectronic devices.

Epitaxial Cu/Fe/Cu trilayers with Fe film thickness between 4 and 110 A have been deposited on the 7×7 reconstructed surface of Si(111) single crystal. The structural and chemical characterization of Fe films was accomplished by in situ low energy electron diffraction, Kikuchi electron diffraction and Auger electron spectroscopy. As the Fe thickness exceeds about 6–8 A, a fcc–bcc phase transition occurs by the appearance of bcc(110) domains in the Kurdjumov–Sachs orientation. The structural transformation is also confirmed by ex situ X-ray diffraction experiments in the θ–2θ configuration. The evolution of the magnetic properties with the Fe film thickness has been studied by means of surface magneto-optic Kerr effect. Hysteresis loops measurements in the longitudinal configuration show a marked increase of the saturation signal which can be associated with the structural fcc–bcc phase transition of Fe.