Magnetic Anisotropy and the Appearance of Stripe Magnetic Domains in Co/Fe Multilayers

Thin Co/Fe multilayers were e-beam evaporated in ultra-high vacuum, keeping constant the Co layer thickness and varying that of Fe in the 0.5÷15 nm range. By increasing the Fe layer thickness, a component of magnetization perpendicular to the film plane rises up, and long and parallel magnetic domains (stripe domains) appear. The phenomenon is explained on the basis of the competition between the magnetoelastic anisotropy induced by stresses at the interfaces, and the shape anisotropy constraining the magnetization in the film plane. This revised version was published online in August 2006 with corrections to the Cover Date.     

High temperature solid state reactivity between iron and chromium monoborides

Powder mixtures of FeB and CrB were compacted and then treated at 1000 C under vacuum for 8 h in order to obtain information on the solid state reactivity of the monoborides, useful to clarify the growth mechanism of boride coatings on chromium steels and to optimize the conditions of the thermochemical process. The effects of diffusion phenomena are pointed out and the relevant mechanisms discussed.     

On the role of Sb excess in Fe–Sb oxides based catalysts

Fe–Sb oxide catalysts with different amounts of Ti were prepared by coprecipitation technique. The stability of the systems is described in terms of the phases formed as a function of the calcination temperature, the Ti content and the use in the reactor.     

Interfacial phenomena and magnetic properties of Fe/Al multilayers of different thickness

Fe/Al thin film multilayers, differing in the thickness of Fe films (30÷10 Å, were electron-beam evaporated in ultra-high vacuum. Interdiffusion and reaction phenomena occurring during deposition at interfaces were studied by means of conversion electron Mössbauer spectroscopy and Auger electron spectroscopy depth-profiling. Magnetic behavior was investigated by alternating force gradient magnetometry. The formation of Fe–Al solid solution and intermetallic compound is observed. Multilayers are ferromagnetic with magnetization in the film plane for iron film thickness ?15 Å, while exhibiting a superparamagnetic behavior at 10 Å.     

Ferromagnetic Planar Nanocomposites

Hyperfine Interactions - Modern permanent magnets require a high coercive field on account of a strong magnetocrystalline anisotropy, as well as a high saturation magnetization and high Curie...     

On the Phase Transformations in Cr–FeB and Fe–CrB Systems at High Temperature

The solid state interactions occurring at high temperature in the Cr–FeB and Fe–CrB systems were studied by transmission Mössbauer and X-ray diffraction techniques on samples prepared by powders carefully mixed, cold-compacted and then treated at 1000°C for times up to 16 h. In the Cr–FeB system, iron atoms liberated by the substitutional diffusion of Cr into FeB lattice preferentially destabilize the iron monoboride with formation of Cr-containing Fe₂B. In the Fe–CrB system, chromium atoms liberated by the substitutional diffusion of Fe into CrB lattice interacts with iron forming an Fe–Cr metal alloy. Moreover, zones of Cr-containing FeB and Fe₂B form at the contact between metal iron and chromium monoboride, and tend to disappear as iron is consumed by the alloying process.     

Phase Composition of Oxidised Layers Grown on Steel Exposed to Liquid Lead at 749 K

The corrosion resistance of AISI 316 LN stainless steel was studied in contact with stagnant, oxygen-saturated liquid lead at 749 K for times up to 1200 h. The reaction products were analysed by means of optical and scanning electron microscopy, electron probe microanalysis, X-ray diffraction analysis and Mössbauer spectroscopy. Thin layers of largely variable thickness formed on the surface, mainly consisting of Fe₃O₄, with small amounts of FeO in the inner regions, Fe₂O₃ and an Fe-Pb-O ternary product in the outermost regions. The alloying elements Cr and Ni diffused to a different extent into Fe₃O₄. A mechanism is proposed to explain formation and growth of the reaction products.

     

Influence of the Interfacial Characteristics on the Tribological Behaviour of TiN-Base Films on Iron

The dry sliding behaviour of TiN-base films deposited onto a tool steel by two different physical vapour deposition techniques is discussed on the basis of the characteristics of both coatings and interfacial regions. It is shown that film adhesion is determining for the wear resistance. Other important factors are the film hardness and the intensity of the stress state at the film-substrate interface.     

Aging of Fe−Al thin film multilayers

Multilayers constituted by very thin films of Fe and Al, deposited by thermal evaporation and magnetron sputtering techniques and then aged in air at temperatures in the 300–400 K range for times up to 200 h, were analyzed by means of XRD, CEMS, XPS and AES measurements. Fe(Al) solid solutions form during evaporation because of interdiffusion phenomena at the Fe–Al interfaces, while Al undergoes oxidation during sputtering deposition and, consequently, the multilayers are constituted by Fe intercalated with Al₂O₃ films. Aging treatments in oxidizing environments induce no significant modification in sputtered multilayers while, on the contrary, the evaporated multilayers show the effects of both interdiffusion and oxidation phenomena.     

Co/Fe Multilayers as Planar Magnetic Nanocomposites

Co/Fe multilayers were electron beam evaporated in ultra-high vacuum and analyzed by Alternating Gradient Force Magnetometry, Magnetic Force Microscopy, Conversion Electron Mössbauer Spectroscopy, and Transmission Electron Microscopy. The multilayer of 10 nm Co and 30 nm Fe layer thickness showed a single-phase magnetic behavior because of a strong exchange coupling established between the layers. The system exhibits stripe domains which were correlated to the presence of a perpendicular magnetic anisotropy. The study performed on multilayers where Co was intercalated by very thin ⁵⁷Fe layers showed that the interfaces were very clean and sharp.