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International audience; A series of (Nd1-xSmx)Fe11Ti alloys with the ThMn12 crystal structure have been fabricated and characterized in order to promote a strong uniaxial anisotropy in NdFe11Ti without the need of nitrogenation. The compounds show small changes in the lattice parameters and cell volume, as well as Curie temperature and spontaneous magnetization. The anisotropy field, however, rapidly increases with the incorporation of Sm and overcomes the effect of nitrogenation, reaching values > 4 T for a 30% Sm content. Mössbauer spectroscopy indicates that the quadrupole splitting is correlated with the magnetic anisotropy. These alloys are good candidates for permanent magnets, provided the correct microstructure is developed to increase coercivity.

International audience; Nd(1-x)Zr(x)Fe10Si2 alloys have been prepared in the tetragonal ThMn12-type structure by arc-melting and melt-spinning and then nitrogenated to improve their magnetic properties. For x = 0.4 and 0.6 the Curie temperature and magnetic anisotropy fields increase from 280-300 ºC to about 390 ºC and from 2.8-3 T to 4.5-5 T respectively. The saturation magnetization remains almost unchanged. The nitrogenated powders were processed by spark plasma sintering (SPS) leading to compact pellets, which retain the full nitrogen content and magnetic properties up to 600 ºC, but segregated Fe-Si at elevated temperatures. Nitrogenation and SPS processing are, therefore, appropriate for sintering metastable materials such as (Nd,Zr)Fe10Si2 into compact material without loosing functional properties. This opens a way towards a new family of permanent magnets, lean of critical raw materials.

International audience; Inclined, zigzag andspiral Ti1-xCux films wereco-sputtered by theGlancing Angle Deposition technique. Two distincttitanium(Ti)andcopper(Cu)targetswereusedandthefilmsweregrownwithaparticleflowincidence angle α of 80°. The thin films had Cu contents ranging from 36 to 76 ± 5at. %. The effect of increasing Cu incorporation on the electrical anisotropy, as well as the effect of columnar architecture variations on the morphological,structuralandelectricalpropertiesofthefilmswasevaluatedandcorrelatedwiththeparticular theirarchitectures. Mainresultsshowwell-definedandhighlyinclinedcolumns(withanaveragecolumnangleβ=45° ± 5°) forallsputteringconditions.Quasi-amorphousthinfilmswereobtainedwithlowCucontents(36at.%),while crystallineCu(111)+Ti3Cu(114)bi-componentstructureswereachievedathighCuconcentrations(76at.%). No permanent oxidation of the films was detected after a two-cycle RT-200°C-RT (RT – room temperature) annealinginair.Thetwo-dimensionalrepresentationoftheresistivityanisotropyofthecolumnarand2zigzags filmsisshapedasanelongatedellipsealongthexxdirection,withavariationoftheeffectiveanisotropy,Aeff,at 200°C from 1.4 to 2.9. The samples prepared with 2 spirals and the same Cu content (36at. %) exhibit an isotropicbehavior,withanAeffvalueat200°Cof1.1.Theoverallresultsdemonstratethepossibilitytotunethe thinfilms'morphologyandelectricalcharacteristicsinordertoobtainasetofpropertiesthataresuitableforthe developmentofhighperformancematerials,suchasthecaseofresistancetemperaturedetectors.

International audience; Inclined, zigzag and spiral TiAg films were prepared by glancing angle co-deposition, using two distinct Ti and Ag targets with a particle incident angle of 80° and Ag contents ranging from 20 to 75 at%. The effect of increasing Ag incorporation and columnar architecture change on the morphological, structural and electrical properties of the films was investigated. It is shown that inclined columnar features (β = 47°) with high porosity were obtained for 20 at% Ag, with the column angle sharply decreasing (β = 21°) for 50 at% Ag, and steeply increasing afterwards until β = 37° for the film with 75 at% Ag. The sputtered films exhibit a rather well-crystallized structure for Ag contents ≥50 at%, with a TiAg (111) preferential growth. No significant oxidation was detected in all films, except for the one with 20 at% Ag, after two 298–473–298 K temperature cycles in air. The calculated temperature coefficient of resistivity (TCR) values vary between 1.4 and 5.5 × 10−4 K−1. Nano-sculptured spiral films exhibit consistently higher resistivity (ρ = 1.5 × 10−6 Ω m) and TCR values (2.9 × 10−4 K−1) than the inclined one with the same Ag content (ρ = 1.2 × 10−6 Ω m and TCR = 2.0 × 10−4 K−1). No significant changes are observed in the zigzag films concerning these properties. The effective anisotropy A eff at 473 K changes from 1.3 to 1.7 for the inclined films. Spiral films exhibit an almost completely isotropic behavior with A eff = 1.1. Ag-rich TiAg core + shell Janus-like columns were obtained with increasing Ag concentrations.

This work reports on the preparation and characterization of Zinc Oxide (ZnO) thin films, exploring their anisotropic electrical resistivity behaviour evolution as a function of the different preparation conditions. Results show that by increasing the oxygen content in the work gas flow, the electrical resistivity increases from about 2.4 x 10(-2) Omega.cm (common in fairly conductive-like materials) to values in order of M Omega.cm, which is typical of materials that vary from semiconducting to roughly insulating type. Regarding the thin films structural behaviour, a relatively clear evolution of the preferential growth becomes clear when preparing the films within the three different regimes. The X-ray diffraction (XRD) patterns revealed the development of a polycrystalline hexagonal-like structure, confirmed by the presence of dominant and very intense ZnO (002) and ZnO (101) diffraction peaks. A change in preferential growth was noticed with the change in the preparation conditions.By in-air annealing the samples from room temperature (RT) up to 200 degrees C and cooling down to RT again, the differences between the resistivity values along the xx and yy directions become significant, a clear sign of the anisotropic nature of the films. The anisotropy obtained during the annealing cycles of the films increased from 0.98 to 1.10 and, consequently, the Temperature Coefficient of Resistance, TCR, increased in both xx and yy directions, from TCRxx (and yy) similar to 9.0x10(-4) to TCRxx = 6.82 x 10(-3) and TCRyy = 5.97 x 10(-3) degrees C-1. Important also to note is that the increase of the grain size of the films showed to have a significant effect in the effective anisotropy, revealing to be a major factor to take into account., This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013 and project PTDC/EEI-SII/5582/2014 and by the Region of Franche-Comte, the French RENATECH network and performed in cooperation with the Labex ACTION program (contract ANR-11-LABX-01-01). A. Ferreira thanks the FCT for grant SFRH/BPD/102402/2014. Financial support from the Basque Government Industry Department under the ELKARTEK Program is also acknowledged., info:eu-repo/semantics/publishedVersion

The polyol route is a versatile and up-scalable method to produce large batches of iron oxide nanoparticles with well-defined structures and magnetic properties. Importance of parameters such as temperature and reaction time, heating profile, nature of the polyol solvent or organometallic precursors on nanostructure and properties has already been described in the literature. Yet, the crucial role of water in the forced hydrolysis pathway has never been reported, despite its mandatory presence for nanoparticle production. This communication investigates the influence of the water amount and temperature at which it is injected in the reflux system for either a pure polyol solvent system or a mixture with poly(hydroxy)amine. Distinct morphologies of nanoparticles were thereby obtained, from ultra-ultra-small smooth spheres down to 4 nm in diameter to larger ones up to 37 nm. Well-defined multicore assemblies with narrow grain size dispersity termed nanoflowers were also synthesized. A diverse and large library of samples was obtained by manipulating the nature of solvents and the amount of added water while keeping all other parameters constant. The different morphologies lead to magnetic nanoparticles suitable for important biomedical applications such as magnetic hyperthermia, magnetic resonance imaging (MRI) contrast agent, or both.

(Mn,Co)WO4compounds are regarded as reference spin-induced multiferroics. A comparative study is presented here, within the magnetic symmetry framework, of the incommensurate magnetic orders responsible for the ferroelectric phases of (i) MnWO4under a magnetic field (H||b) and (ii) Mn0.90Co0.10WO4in the absence of an external field. On the one hand, although these two ferroelectric phases are stabilized under different external physical conditions, both present the sameXc1′(α0γ)ssmagnetic symmetry and practically the same modulation vector. The magnetic ordering in both phases is an elliptical helix with the magnetic moments (as the polarization vector,P) perpendicular to thebaxis, although in most of the ferroelectric compositions of the (Mn,Co)WO4family the spins rotate in planes containingb(and haveP||b). On the other hand, the anisotropy of the resulting magnetic modulations is extraordinarily different in the two phases. This is described and explained in the light of the different anisotropies of Co and Mn ions.