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The one-dimensional coordination polymer, self-assembled from bis­(acetyl­acetonato)cobalt(II) units as metal–complex connectors and 1,4-di­aza­bicyclo­[2.2.2]octane (DABCO) as linkers, can serve for a comparative investigation of the magnetic behaviour of analogous compounds. Space filling more symmetric than atom positions leads to pronounced orientational disorder for the DABCO ligand., The title compound, [Co(C5H7O2)2(C6H12N2)]n, was obtained as a one-dimensional coordination polymer from bis­(acetyl­acetonato)di­aqua­cobalt(II), [Co(acac)2(OH2)2], and 1,4-di­aza­bicyclo­[2.2.2]octane (DABCO), a di­amine with good bridging ability and rod-like spacer function. In the chain complex that extends along the c axis, the CoII atom is six-coordinated, the O-donor atoms of the chelating acac ligands occupying the equatorial positions and the bridging DABCO ligands being in trans-axial positions. In the crystal structure, the DABCO ligand is conformationally disordered in a 50:50 manner as a result of its location across a crystallographic mirror plane. The metal–metal distance is very close to that in a related compound exhibiting weak anti­ferromagnetic exchange between the CoII ions, and the title compound can thus be useful for obtaining more information about the contribution of different bridges to the magnetic coupling between paramagnetic ions.

Magnetic properties of carbon nanotubes (CNT) obtained by plasma-enhanced chemical vapour deposition (PECVD) have been studied. The growth of these nanotubes has been activated from Ni catalyst nanoparticles. Samples consist of Ni nanoparticles encapsulated at the tip of vertically aligned multiwalled carbon nanotubes (VACNTs) forming an homogeneous and dense large area monolayer of isolated (non-contacting) nanoparticles. The magnetic characterisation has been performed in the temperature range of 5-300 K with magnetic fields up to 9 T. The results show that the wide size range (30-180 nm) of the particles originates the coexistence of blocked and superparamagnetic particles and leads to the strong ferromagnetic behaviour of the whole assembly. The coercivity decreases monotonically with increasing temperature and the value for the intrinsic coercivity is 225 Oe. The encapsulation of Ni nanoparticles by VACNTs preserves them from aggregation. This makes possible to tune the coercivity by controlling size distribution of particle monolayers. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. This work was supported in part by the University of Oviedo under Grant No. UNOV-08-MA-100 and by the Spanish MEC through grant Ref. MAT2008-06784. Projects CSD2006-12 and DPI2006-03070 of the Spainsh MEDU and the Generalitat de Catalunya (project No. SGR2005-00666). The authors thank Serveis Cientifico-Tècnics of the Universitat de Barcelona (SCT-UB) for measurement facilities.

We describe the preparation, crystal structure determination, magnetic and transport properties of two novel Mn-containing perovskites, with a different electronic configuration for Mn atoms located in B site. Ca3Mn 3+ 2WO9 and Ca3Mn 3+/4+ 2NbO9 were synthesized by standard ceramic procedures; the crystallographic structure was studied from X-ray powder diffraction (XRPD) and neutron powder diffraction (NPD). Both phases exhibit a monoclinic symmetry (S.G.: P21/n); Ca3Mn 2WO9 presents a long-range ordering over the B sites, whereas Ca3Mn2NbO9 is strongly disordered. By >in-situ> NPD, the temperature evolution of the structure study presents an interesting evolution in the octahedral size (〈 Mn-OâŒ) for Ca3Mn2NbO9, driven by a charge ordering effect between Mn3+ and Mn4+ atoms, related to the anomaly observed in the transport measurements at T≈160 K. Both materials present a magnetic order below TC=30 K and 40 K for W and Nb materials, respectively. The magneto-transport measurements display non-negligible magnetoresistance properties in the paramagnetic regime.© 2013 Published by Elsevier Inc. All rights reserved., C.A.L. and M.E.S. thanks a CONICET fellowship. J.C.P. thanks CONICET (Project PIP 2008-01360), SECyT-UNSL (Project 7707 and Project 2-1612). R.D.S. acknowledges financial support of ANPCYT (Project PICT 2011-0752) and SEPCyT-UNCu (06/C389). J.C.P. and R.D.S are member of CONICET. J.A.A. acknowledges the financial support of the Spanish Ministry of Education to the project MAT2010-16404.

Polyaniline/Fe3O4 nanocomposites were prepared by a one-pot synthesis using N-(4-aminophenyl)aniline as the reagent, molecular oxygen or hydrogen peroxide as the oxidizing agents in the presence of Fe3O4 nanoparticles (NPs) in powder and ferrofluid form. Both magnetic NPs in powder and ferrofluid form showed similar catalytic behaviour. The catalytic effect is particularly evident when molecular oxygen was used as the oxidizing agent. However, concerning the morphological aspects, only the composites prepared in the presence of ferrofluid-type Fe3O4 NPs showed a preferential morphology of nanorods (between 30 and 110 nm in diameter). All the composites are superparamagnetic at room temperature but at low temperature they are in a blocked state. Inter-particle interactions significantly affect the magnetic properties of the composites. The electrical conductivity of the composites is about 10−2 S cm−1, in agreement with the values obtained for polyaniline prepared by chemical route. A mechanism of the nanorods formation is proposed.

In order to better understand the interesting magnetic behaviour found in the Rare Earth-transition metal/(spacer)/transition metal multilayers, a multilayer of Co/[Si/Gd0.36Co0.64/Si/Co]4/glass was studied by SQUID magnetic measurements and polarized neutron reflectivity. A model for the magnetic profile of the sample was proposed, which fitted well the polarized neutron reflectivity measurements at different magnetic states: ferrimagnetic/antiparallel state, under an applied field of 55 Oe, canted states (315 and 675 Oe) and saturation state (1700 Oe). It was found that even at the expected collinear states (ferrimagnet and saturation states), the magnetization was not totally collinear and there was a small component of the magnetization perpendicular to the applied field. Cajastur;FICYT;Gijon City Council;MICINN;Tekniker;University of Oviedo

Köçkar, Hakan (Balikesir Author), The influence of electrolyte pH and cathode potential on the magnetic properties of single layer Nickel films electrodeposited on polycrystalline titanium substrates was studied. The films were deposited at the electrolyte pH=3.5 +/- 0.1, 2.5 +/- 0.1 and 2.1 +/- 0.1 by varying the deposition potentials (-1.2, -1.5 and -1.8 V vs saturated calomel electrode, SCE) applied in continuous waveform. The structural analysis by X-ray diffraction revealed that the films have face-centred cubic structure. Results of the magnetic measurements obtained by vibrating sample magnetometer (VSM) indicated that the magnetic properties were affected by the electrolyte pH and the cathode potentials in terms of magnetic anisotropy. At the highest pH the films deposited at the lowest potential had in-plane magnetic anisotropy. As the electrolyte pH decreased from the high (pH=3.570.1) to low (pH=2.5 +/- 0.1), which is aided by increasing the potentials, resulted in an almost magnetic isotropy in the films. However, isotropic magnetic behaviour was observed for the film deposited at the low pH combined with the high potential (-1.8 V vs SCE). Magnetic thickness profile of the samples obtained by VSM revealed that the isotropic films have a smoother magnetic variation across the film from one edge than the anisotropic ones. This is also verified with a microscopic observation by an optical microscope and the surface of the isotropic films is observed to be smoother than that of the anisotropic ones. Furthermore, all films were found to have planar magnetic anisotropy irrespective of the pH's and the potentials.

We report the temperature and filed dependence of magnetic behaviour of the Ho1-xMmxCo2 (x = 0, 0.1, 0.2, 0.3 and 0.4; Mm = mischmetal) alloys and their crystalline hydrides. The change of magnetic transition temperature (TC), order of magnetic transition and total magnetization of the alloys with increasing Mm content is studied. The alloys exhibit strong composition and field dependence of thermal hysteresis and spin-reorientation below TC. The effect of hydrogen absorption on the magnetic behaviour of alloys is studied, and the results are correlated to the unit cell volume expansion and decrease in the conduction electron density. � 2010 Elsevier B.V. All rights reserved.

Exhibiting rich magnetic behaviour and potentially multiferroic properties, the dugganites, a Te(6+) containing subgroup of the langasite series, are an attractive family of compounds for future study. It was recently shown that Pb-bearing members of the dugganite series undergo distortions away from the P321 symmetry that is characteristic of the langasites. Here, we detail the consequences these distortions have on the magnetism exhibited by Pb3TeCo3V2O14 and Pb3TeCo3P2O14, solving the magnetic structures of both compounds with respect to a new supercell. Using neutron scattering and magnetic susceptibility measurements, we show that small applied magnetic fields can seriously perturb the delicate magnetic states in both of these systems. This is further demonstrated by presenting how doping P(5+) onto the nonmagnetic V(5+) site completely changes the magnetic structure from either of the end series members. Finally, it is shown using inelastic neutron scattering and magnetic susceptibility measurements that Pb3TeCo3V2O14 can be characterized using a model for isosceles trimers, which do not exist in the previously reported P321 subcell.

International audience; The prediction of core losses in a rotating electrical machine generally requires a numerical approach (finite element or integral method). However, the magnetic characteristics obtained through a standard Epstein facility and inserted in the numerical models predict losses which are quite different from those obtained experimentally. This difference can be partly explained by the presence of plastic strain close to the cutting edge of manufactured motor sheets. In the present paper, numerical functions are first established to predict the change in the magnetisation and loss curves with respect to the plastic strain level. Second, a microhardness test is used to measure the local plastic strain directly on the manufactured sheet. Finally, relations are obtained between the main magnetic properties and the position on the sheet: the resulting magnetic property profiles allow the numerical approach to be improved.

The magnetic behaviour in Dy1-xMmxCo2 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5; Mm = mischmetal) compounds is reported using temperature and field dependence of magnetization (M-T and M-H respectively) measurements. A strong composition dependent irreversibility is observed in both the M-T and M-H scans below the magnetic ordering temperature (TC). A clear change of the first-order magnetic transition of DyCo2 to a second-order one in Dy0.5Mm0.5Co2 is evidenced by M-T and a series of Arrott (M2 versus H/M) plots, obtained from the M-H isotherms around TC. The variation in induced moments of the Co sublattice is estimated. It is found that the Mm substitution can only lead to a considerable reduction in the TC, saturation magnetization, and Co moment. The observed behaviour of M-T and M-H plots with increasing Mm content is discussed in detail. � 2010 IOP Publishing Ltd.