Onderzoek naar de diffusie in het systeem chroom-wolfraam

Applied Science

Magnetic coupling in sputtered Fe/Si-type multilayers

In HV-sputtered Fe100-xSix/Si100-yFey multilayers the antiferromagnetic coupling strength and the fraction of ferromagnetic coupling increases with decreasing temperature. The ferromagnetic component can be explained by bridging along grain boundaries or by an Fe percolation mechanism in the nonmagnetic interlayers. Recent speculations that the magnetic coupling across the FeSi spacers is mediated by thermal excitation of charge carriers are incompatible with our observations

Comment on "magnetoresistance associated with antiferromagnetic interlayer coupling spaced by a semiconductor in Fe/Si multilayers"

A Comment on the Letter by K. Inomata, K. Yusu and Y. Saito, Phys. Rev. Lett. 74, 1863 (1995).</p

Magnetic anisotropies in Co/NI(111) multilayers

The magnetic anisotropy and the saturation magnetization have been investigated in several series of Co/Ni multilayers, with relatively thick Co and Ni layers, grown in ultrahigh vacuum (UHV) and high vacuum (HV) by vapor deposition. The volume and interface contributions to the magnetic anisotropy were determined from magnetization measurements. The Co/Ni interface contribution was found to favor perpendicular anisotropy. A series of 2 Å Co/4 Å Ni multilayers, grown in HV, exhibited an easy axis perpendicular to the layer planes, as evidenced both by polar Kerr rotation and ferromagnetic resonance (FMR) measurements. The first- and second-order anisotropy constants were determined from FMR. Indications were found that the presence of FMR signals in (perpendicular easy) samples with low magnetic sublayer thicknesses depends on the magnitude of the surface anisotropy and on the amplitude of fluctuations in the magnetic layer thicknesses.</p

The temperature dependence of the magnetization of magnetic multilayers

The magnetization of Co/Pt and Co/Au multilayers has been measured as a function of temperature. For the Co/Pt multilayers with fixed cobalt sublayer thickness of 4, 6 and 8 Å, the magnetization decreases faster with temperature as the platinum layers are made thicker. In contrast the magnetization of the Co/Au multilayers is nearly independent of the Au thickness in a range from 8 to 40 Å with a Co thickness of 6 Å and remain almost constant up to 500 K. Interlayer coupling and interdiffusion are discussed as possible causes for the observed behaviour

Perpendicular anisotropy in palladium/cobalt multilayers

The anisotropy values in polycrystalline Pd/Co multilayers with [111] texture as determined from magnetization measurements, torque measurements, and ferromagnetic resonance are compared. It is concluded that the most reliable value is obtained from the area between the magnetization curves measured with the field parallel and perpendicular to the plane of the film. The anisotropy is made up of a volume and an interface contribution. In a pair interaction model for the interface anisotropy it is shown that the latter is very sensitive to the precise distribution of Co and Pd at the interfaces. From the experimental data we derive a lower bound value of 0.2 meV per Co atom for the energy change with the direction of the magnetic moment. The temperature dependence of the magnetization indicates a long-range interaction across the Pd layers up to 15–25 Å

Metallische multilagen

De mogelijkheid om kunstmatig op atomaire schaal de structuur en samenstelling van de vaste stof te manipuleren, is een belangrijke wens van veel vaste-stoffysici en materiaalkundigen. Men spreekt dan graag over ‘atomic engineering’. In de halfgeleiderfysicia heeft de beheersing van de groei van dunne lagen niet alleen geleid tot technisch belangrijke doorbraken (zoals de vaste-stoflaser), maar ook tot de observatie van nieuwe verschijnselen zoals bet quantum-Hall-effect. Ook voor andere maierialen komen er steeds meer mogelijkheden om dunne lagen met een van te voren bepaald samenstellingsverloop te maken. Hoewel de preparatie van deze in compositie gemoduleerde structuren nog in een primitief stadium verkeert, zijn al verschillende opzienbarende resultaten behaald op bet gebied van magnetis me, supergeleiding, vaste-stofreacties, diffusie, elastisch gedrag en ontwikkeling van nieuwe materialen. In deze bijdrage willen we een globaal overzicht geven van een aantal ontwikkelingen op bet gebied van bet maken van metallische multilagen en de fysische verschijnselen daarin, waarbij bet accent zal liggen op magnetisch gedrag en supergeleiding

Magnetic interface anisotropy in Pd/Co and Pd/Fe multilayers

Pd/Co and Pd/Fe multilayer thin films containing ultrathin (2-12 Å) Co and Fe layers were prepared by vapour deposition in ultrahigh vacuum. Their magnetization was measured at room temperature in fields parallel and perpendicular to the film plane. The Pd/Co multilayers show a transition of the preferred direction from lying in the film plane towards lying along the film normal when decreasing the Co layer thickness below 8 Å. The Pd/Fe multilayers are preferably magnetized in the film plane, although the anisotropy decreases with lower Fe layer thickness. The magnetic anisotropy of both types of films can be interpreted by assuming an interface contribution which favours a perpendicular magnetization, and a volume contribution which favours an in-plane magnetization. The magnitude of the volume contribution is discussed in terms of magnetostatic, magnetocrystalline and magnetoelastic anisotropies, and equals, surprisingly, the anisotropy of the ferromagnetic elements in bulk thin film form in both cases

Magnetic properties and structure of palladium/cobalt and palladium/iron multilayers

Pd/Co and Pd/Fe multilayer films containing ultrathin Co and Fe layers were prepared by vapor deposition on substrates at room temperature. Their modulated structure, even for films containing 2-Å-thin Co and Fe layers, was proved by x-ray diffraction and transmission electron microscopy. Below a Co layer thickness of about 8 Å, the Pd/Co multilayers acquire an easy magnetic axis perpendicular to the film, which is mainly caused by magnetic interface anisotropy. This leads for multilayers containing Co monolayers to almost rectangular hysteresis loops, by which these films may be very suitable as a perpendicular magnetic recording medium. Pd/Fe multilayers also have a perpendicular interface anisotropy, but the shape anisotropy dominates. Per unit Co volume the Pd/Co multilayers have a higher saturation magnetization than pure Co, which is attributed to an induced ferromagnetism on Pd interfacial atoms