A secondary neutral mass spectrometric ͑SNMS͒ depth profile study of electrodeposited Co/Cu multilayers was performed. Depth profile measurements were performed both in the conventional way ͑i.e., starting the sputtering from the final deposit surface͒ and in the reverse manner ͑i.e., detaching the multilayers from the substrate and starting the analysis from the substrate side, which was very smooth as compared to the final deposit surface͒. The latter method could yield significantly larger intensity fluctuations in the SNMS spectra. Surface roughness data were measured with atomic force microscopy ͑AFM͒ for multilayers with different bilayer numbers but otherwise exhibiting the same layer structure as those used for the depth profiling. The experimental AFM surface roughness evolution was used to calculate the result of the depth profile measurements quantitatively. An excellent agreement was obtained between this calculation and the SNMS measurements. It was shown that the decrease in the intensity fluctuations during the depth profile analysis stems mainly from the increase in surface roughness of the samples studied, especially in the conventional sputtering mode. It was also concluded that the thickness fluctuation of the entire multilayer deposit and that of each layer are strongly correlated. DOI: 10.1149/1.3133182 .Nanoscale magnetic/nonmagnetic multilayers are in the forefront of materials research since the discovery of giant magnetoresistance ͑GMR͒ in these nanostructures.1,2 Multilayers are mostly produced by physical methods ͑evaporation, sputtering, and molecular beam epitaxy͒, some of them applying a fairly expensive high vacuum system. The feasibility of the electrodeposition of metallic magnetic/ nonmagnetic multilayers with GMR was demonstrated 3 a few years after the discovery of the phenomenon. Although electrodeposition has long been considered as a possible low cost alternative to the physical sample preparation techniques, the quality of the electrodeposited ͑ED͒ multilayers is still inferior to their physically produced analogs. The literature of the ED multilayer films with GMR amounts to some 140 papers, 4-6 but very little is known about why the sample quality, especially GMR, cannot achieve the properties of the samples prepared by physical methods.Although depth profile analysis is a very efficient tool for the characterization of element distribution and the interface quality of ED multilayer samples, only a few studies were published hitherto. Basile et al.7 studied the depth profile of ED Co/Cu sandwiches by Auger electron spectroscopy. They found that the observed interface width of approximately 20 nm is an inherent feature of the sample itself rather than the artifact of the sputtering method used for the depth profiling ͑although the sputtering also leads to some intermixing at a smaller depth scale 8,9 ͒. According to Tokarz et al., 10 the interface width of ED Cu͑200 nm͒/Ni͑200 nm͒ bilayers can also be estimated as being 20-30 nm, as shown by their secondary-ion mass spe...

Magnetocaloric materials with composition of Mn 1.3 Fe 0.65 P 0.5 Si 0.5 have been prepared by ball milling and solid-state reaction methods and consolidated using powder annealing, and conventional and spark plasma sintering. Magnetic and calorimetric measurements show remarkable differences upon first cooling, and slight differences on second and further coolings between the samples prepared by different synthesis routes. Further measurements using Hall probe imaging in high magnetic field have been also carried out. As-prepared samples have been cooled down just above the critical temperature, and the first phase transition has been induced by application of a magnetic field. Bulk samples show staircase isothermal magnetization curves whereas powders show smoother transition curves.

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International audienceDue to the limited rare-earth elements resources, ferrite magnets need to be improved drastically. Ideally, for a true hard magnet, the coercive field should be larger than the saturation magnetization, which is not yet realized for ferrites. Thus, an alternative can be found in making very fine grain ferrite magnets, but it is usually impossible to get small grains and dense material together. In this paper, it is shown that the spark plasma sintering method is able to produce approximately 80% of dense material with crystallites smaller than 100 nm. The as-prepared bulk sintered anisotropic magnets exhibits coercive field of 0.5 T which is approximately 60% of the theoretical limit and only a few percentage below that of loose nanopowders. As a result, the magnets behave nearly ideal (−1.18 slope in the BH plane second quadrant) and the energy product reaches 8.8 kJ m−3, the highest value achieved in the isotropic ferrite magnet to our knowledge

Structural characterization of the Mn1.3Fe0.65P0.5Si0.5 powder is reported. The rare-earth-free magnetocaloric material was prepared by ball milling and solid-state synthesis. X-ray diffraction data were collected in a wide temperature range across the magnetoelastic phase transition. The lattice parameters and volume fractions of the paramagnetic and ferromagnetic phases were determined as functions of temperature using Rietveld fitting. The virgin effect (a delay of the phase transition on first cooling) and associated variation of lattice parameters are analyzed on the assumption of elastic constraints imposed on the paramagnetic phase by the defect structure. A simple Landau model with magnetoelastic coupling illustrates the observed first-order behavior.

Abstract.Anisotropic magnetoresistance (AMR) is the basic phenomenon of a spread class of sensors. AMR effect has a strong mechanical stress dependence. Micromagnetic simulations are often used for modeling the magnetoresistance of ferromagnetic materials, but these approaches do not allow to investigate macroscopic effects (for example behavior of a polycrystal under stress) due to the high number of interactions and degrees of freedom. On the other hand macroscopic phenomenological approaches fail in describing the main role of microstructure on the effective behavior. In this work a micro-macro model is proposed to describe the effect of stress on the AMR in ferromagnetic polycrystals. Results are discussed and compared to experimental data from the literature.

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