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The initial use of ligands 2′-hydroxyacetophenone (HL1), 2-hydroxybenzophenone (HL2) and 2,2′-dihydroxybenzophenone (H2L3) in iron(iii) chemistry is described. The syntheses and crystal structures are reported for five iron(iii) clusters: [Fe10O4(OMe)14(L1)6(MeOH)2](NO3)2·3MeOH (1·3MeOH), [Fe12O4(OH)(OMe)17(L1)8](ClO4)2·2H2O (2·2H2O), [Fe10O4(OMe)14Cl4(L2)4(MeOH)2] (3), [Fe10O4(OMe)14(L2)6(py)2](ClO4)2·MeOH (4·MeOH), where py = pyridine, and [Fe6O2(OEt)6(O2CMe)2(L3)2(HL3)2] (5). The molecular structures of the decanuclear clusters 1, 3 and 4 are organized around a {Fe10(μ4-O)4(μ3-OMe)2(μ-OMe)12}8+ core consisting of ten {Fe3O4} face-sharing defective cubane units. The core of 2 consists of a {Fe12(μ4-O)4(μ3-OMe)4(μ-OH)(μ-OMe)13}10+ unit composed of twelve {Fe3O4} face-sharing defective cubanes. The ligands (L1)− and (L2)− in 1-4 adopt the O,O′-bidentate chelating coordination mode and their roles are to terminate the further aggregation of the FeIII/O2−/RO− cores. Complex 5 contains the {Fe6(μ4-O)2(μ-OEt)6(μ-Ocarbonyl)2}4+ core, where the μ-Ocarbonyl atoms are the bridging carbonyl oxygens of the two η1:η2:η1:μ (L3)2− ligands the (HL3)− groups behave as Ophenolate, Ocarbonyl-bidentate chelating ligands with the neutral hydroxyl group being unbound to the FeIII atoms. The core is composed of four {Fe3O4} face-sharing defective cubanes. The FeIII atoms in 1-5 are all six-coordinate with distorted octahedral geometries. The IR spectra of the complexes are discussed in terms of the known coordination modes of the ligands and the ionic character of nitrates and perchlorates. Variable-temperature magnetic susceptibility and variable-field magnetization measurements establish that 2, 3 and 5 have S = 3, 0 and 5 ground states, respectively. The susceptibility data for 5 were fitted using a 3-J model indicating the simultaneous presence of both antiferromagnetic and ferromagnetic FeIII⋯FeIII exchange interactions. Known magnetostructural correlations in oxido-bridged iron(iii) systems have been applied to rationalise the magnetic behaviour of the three clusters. The results of the present study demonstrate the utility of HL1, HL2 and H2L3 in the stabilisation of robust iron(iii)/oxido/alkoxido clusters. © The Royal Society of Chemistry. 46 10 3240 3251

The dissolution of anhydrous iron bromide in a mixture of pyridine and acetonitrile, in the presence of an organic amine, results in the formation of an [Fe34] metal oxide molecule, structurally characterised by alternate layers of tetrahedral and octahedral FeIII ions connected by oxide and hydroxide ions. The outer shell of the complex is capped by a combination of pyridine molecules and bromide ions. Magnetic data, measured at temperatures as low as 0.4 K and fields up to 35 T, reveal competing antiferromagnetic exchange interactions; DFT calculations showing that the magnitudes of the coupling constants are highly dependent on both the Fe‐O‐Fe angles and Fe−O distances. The simplicity of the synthetic methodology, and the structural similarity between [Fe34], bulk iron oxides, previous FeIII–oxo cages, and polyoxometalates (POMs), hints that much larger molecular FeIII oxides can be made., Fe Maiden: An [Fe34] molecular metal oxide consists of an [Fe4] tetrahedron encapsulated in a [Fe18] truncated tetrahedron, face‐capped by four [Fe3] triangles, and is characterised by alternate layers of tetrahedral and octahedral Fe ions linked by oxide and hydroxide anions.

A highly topical set of materials are those ABO3 perovskite oxides, in which multiferroicity is chemically engineered by placing ferroelectrically and magnetically active cations in A- and B-site, respectively. This is the case of the BiFeO3 and BiMnO3 perovskites, and also of the solid solutions they form with PbTiO3. Interest in these binary systems is fostered by the presence of distinctive morphotropic phase boundaries (MPBs), multiferroic in the case of BiFeO3-PbTiO3, for which a high magnetoelectric response has been anticipated. Here, new compositions belonging to the ternary system BiFeO3-BiMnO3-PbTiO3, and specifically along the line that joins the former MPBs, have been prepared by mechanosynthesis to accomplish a thorough analysis of their multiferroic nature. Nanocrystalline powders with a perovskite-type structure were obtained in the entire range of compositions, which all exhibited polymorphic phase coexistence allowing a line of MPBs to be established. The variation of the perovskite structural characteristics along this line has been defined, and correlated with those of the magnetic and electrical properties. A set of novel and promising multiferroic materials have been found for BiFeO3 rich compositions., This work has been founded by the Spanish MINECO (MAT2011-23709). C.M.F-P and H.A. thanks financial support by MINECO (BES 2012-053017) and Ramón y Cajal Programme, respectively. Collaboration between ICMM and ISCR was framed within the COST Action MP0904 SIMUFER.

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.

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.

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.