ABSTRACT
This work presents an analysis of the in-plane magnetization reversal mechanisms of Fe nanowires, with widths from 100 nm to 1 microm, fabricated in epitaxial Au(001)/Fe(001)/MgO(001) thin films by means of focused ion and electron beam lithographies, with either positive or negative resist. The experimental results show that the switching mechanisms and hysteresis are almost exclusively functions of the dimensions of the wires and of the Fe intrinsic properties, with minor influence of the specific fabrication route employed upon optimization of nanostructure parameters in terms of crystallinity and morphology, and well defined and reproducible geometry. The reversal processes evolve from wall pinning at low angles between the applied field and the axis of the wires to basically uniform magnetization rotation at high angles. This behaviour can be described in terms of single spin configurations, thus ruling out the formation of multidomain structures even at high angles. The ability to achieve these high quality and well controlled nanowires allowed us to develop an analytical model, based on uniform magnetization configurations considering just the intrinsic Fe properties and the shape and dimensions of the wires. This simple approach provides a very good qualitative and quantitative agreement with the experimental results, thus evidencing the relatively small role of other extrinsic factors in the magnetization processes.
ABSTRACT
In the present work, a new process for depositing nanoparticle layers onto glass has been developed by using one of the most interesting nanoparticle generation technologies at the moment, which is based on the pyrolysis induced by laser of vapours combined with CVD of the particles onto glass. Nanoparticles prepared by this method were deposited into a hot silica substrate obtaining new nanocomposites with unique properties. The coated glasses present new specific functionalities such as colour, and interesting magnetic and optical properties. Control of the thickness and the iron oxide phase, either magnetic or not, has been achieved by adjusting the experimental conditions. Thus, thickness is controlled by the glass and the precursor temperature, while the iron phase is controlled by the precursor temperature and the nature and the flow of the carrier gas. This process is inexpensive, adaptable to current glass production technologies and takes place at atmospheric pressure.
ABSTRACT
MA 956 superalloy is a ferritic stainless material which develops a fine, dense, and well-adhered alpha-alumina layer upon heat treatment at elevated temperatures. This unique capability makes MA 956 attractive for surgical implants. In this work, the magnetic behavior of the material before and after thermal oxidation treatment required to develop the alumina layer is investigated. The thermal oxidation treatment yields a microstructure of elongated grains and a significant change in the texture. Despite these strong microstructural differences between the as-received and heat-treated materials, the hysteretic behavior is not greatly affected by them. MA 956 is a soft magnetic material irrespective of the material condition. The coercive force and residual magnetization of the material are somewhat lower under heat-treated conditions than in the as-received condition.
