Thermal stability of ultrasoft Fe–Zr–N films

The thermal stability of nanocrystalline ultrasoft magnetic (Fe98Zr2)1−xNx films with x = 0.10–0.25 was studied using thermal desorption spectrometry, positron beam analysis and high resolution transmission electron microscopy. The results demonstrate that grain growth during the heat treatment is accompanied by an increase of the free volume and nitrogen relocation and desorption. All these phenomena can drastically degrade the ultrasoft magnetic properties. The nitrogen desorption has already started at temperatures around 400 K. Nevertheless, most of the nitrogen leaves the sample at a temperature above 800 K. We found that nitrogen out-diffusion is significantly retarded compared with the prediction of the diffusion in bulk α-Fe. A qualitative model is proposed in which the nitrogen out-diffusion in nanocrystalline material is retarded by trapping at immobile defects, namely Zr atoms, and also by voids at grain boundaries. From a certain temperature, nitrogen migrates from the interior of the nanograins to the nanovoids at the grain boundaries and the out-diffusion to the outer surface is controlled by transport between the voids.

Temperature effects on nitrogen diffusion and hardness of aluminium surface implanted with nitrogen

This paper is devoted to the study of the surface hardness of pure Al implanted with molecular nitrogen of energy 100 keV. The experiments reported here were designed with a specific problem in mind; that of searching for the perfect implantation dose and temperature combination which could produce the highest increase in hardness. Implantations carried out at low dose and temperature produce a high density of small AlN precipitates, while those carried out at high temperature produce large but few precipitates. Since the mechanical properties are directly related to the dispersion and the size of the AlN precipitates, we can control their effect by varying the implantation conditions. Samples were successively implanted with 14N and 15N at different doses (1-3 × 1017 at cm-2) and temperatures (30-400°C) for each species. Their depth profiles were measured with the resonant nuclear reaction 15N(p,αy)12C. The top surface of the sample was characterized by plane-view transmission electron microscopy and the mechanical properties were studied using a nanoindenter.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Effects of topography on the local variation in the magnetization of ultrasoft magnetic films:a Lorentz microscopy study

This paper concentrates on a detailed analysis of Lorentz transmission electron microscopy (LTEM) observations in the study of the magnetic properties of soft magnetic films. Besides ripple fringes in the LTEM image that are commonly observed in nanocrystalline soft magnetic films, there also appears a dotted contrast along the ripple fringes. A theory of LTEM images for films with one-dimensional and two-dimensional (2D) periodic topographies, in combination with the micromagnetic oscillations of the magnetization, is presented. The theory predicts the 2D pattern in LTEM in agreement with experimental observations