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Magnetic
Terms modified by Magnetic Selected AbstractsEight-Coordinate Endohedral Rhenium, Osmium and Iridium Atoms in Rare-Earth Halide Cluster ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2010Sina Zimmermann Abstract Endohedral (interstitial) atoms are essential for almost all of the rare-earth halide cluster complexes. Most of these contain octahedral clusters, some are isolated, but the majority exhibits condensation by common edges to structures of higher dimensionality. Higher coordination numbers of the endohedral atoms are rare. Four examples of extended cluster complexes with eight-coordinate endohedral atoms of sixth-period elements (Re, Os, Ir) are presented. In the quasi-isostructural, non-isotypic halides {ReGd4}Br4 and {OsSc4}Cl4, square antiprisms of gadolinium and scandium atoms, respectively, are connected by two common faces to chains, surrounded and loosely connected by halogenido ligands. The Re and Os atoms build a slightly bent chain with only little bonding interactions. Chemical bonding is dominated by endohedral atom,cluster atom and cluster atom,halide interactions. The same is true for the two scandium bromides {Ir3Sc12}Br16 and {Os3Sc12}Br16Sc, which contain chains of face-sharing square antiprisms and cubes in a ratio of 2:1. Metal,metal bonding is attested by short distances between those endohedral Ir and Os atoms, respectively, which center the square antiprisms (283 pm and 290 pm, respectively). Magnetic and conductivity measurements on {Ir3Sc12}Br16 reveal paramagnetism and a small-band-gap semiconductor. This is in accord with electronic structure calculations. [source] Magnetic and Electrochemical Properties of a Heterobridged ,-Phenoxido,,1,1 -Azide Dinickel(II) Compound: A Unique Example Demonstrating the Bridge Distance Dependency of Exchange IntegralEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2009Rajesh Koner Abstract The synthesis, structure, magnetic and electrochemical properties of the heterobridged ,-phenoxido,,1,1 -azide dinickel(II) compound [NiII2(HL1)3(,1,1 -N3)]·3H2O (1) derived from the tetradentate Schiff base ligand N -(2-hydroxyethyl)-3-methoxysalicylaldimine (H2L1) are described. The title compound crystallizes in the triclinic system (space group P). Electrochemical analyses reveal that compound 1 exhibits two-step quasireversible couples in the reduction window with E1/2 values of ,1412 and ,1762 mV. The variable-temperature (2,300 K) magnetic susceptibilities at 1 T of the title compound were measured. The interaction between the metal centres is weak ferromagnetic (J = 5.0 cm,1, g = 2.23, D1 = 29.2 cm,1 and D2 = 10.7 cm,1). Comparison of the exchange integral of 1 with that of the only reported ,-phenoxido,,1,1 -azide dinickel(II) compound results in the emergence of a unique example of the dependence of strength of magnetic exchange interaction on the metal,ligand bridge distance. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Single End-to-End Azidocopper(II) Chain Based on an Electroactive Ligand: A Structural, Electrochemical, Magnetic and Ab Initio StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 31 2009Guillaume Pilet Abstract By combining azide and the (Z)-1,1,1-trifluoro-4-(quinolin-8-ylamino)but-3-en-2-one enaminone ligand, HL, an azido-bridged copper(II) one dimensional polymer was synthesized in a one-pot reaction. The solved and refined crystal structure evidenced the unusual single and asymmetric end-to-end coordination mode of the azide ion. The redox properties of this complex were studied by cyclic voltammetry, andoxidation of the azido bridge was evidenced. Magneticmeasurements, combined with magnetostructural-driven analysis revealed a weak ferromagnetic interaction between the copper(II) ions within the N3, -bridged chains, complemented by an antiferromagnetic interaction between the chains mediated by ,,, interactions. A survey of the scarce literature of single end-to-end azido bridges, associated with quantum chemical ab initio calculations, was carried out to tentatively identify the relevant parameters driving the weak intrachain exchange interaction.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Optical, Magnetic and Structural Properties of the Spin-Crossover Complex [Fe(btr)2(NCS)2]·H2O in the Light-Induced and Thermally Quenched Metastable StatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 36 2007Vincent Legrand Abstract [Fe(btr)2(NCS)2]·H2O [btr = 4,4,-bis(1,2,4-triazole)] is thearchetype of highly cooperative and low-dimensional spin-crossover complexes, which exhibit low-spin (LS) to high-spin (HS) light-induced conversion at very low temperature. The structural reorganizations related to the light-induced and thermally induced LS,HS transitions were characterized by single-crystal X-ray diffraction below the relaxation temperature (T = 15 K < TLIESST) and at 130 K within the thermal hysteresis loop. We show that the LIESST and thermal spin transitions lead to the same structural variations, namely an elongation of the Fe,N bonds by 0.18 Å (Fe,NNCS) and 0.20 Å (Fe,Nbtr), on going from LS to HS, together with a reorientation of the NCS group by nearly 13°. The atomic displacement amplitudes, derived from the crystal structures, indicate lattice vibration modes of larger amplitudes and correlatively lower vibration frequencies in the HS state. The deformation of the crystal lattice as a function of temperature and laser excitation was quantitatively analyzed in terms of the HS and LS thermal-expansion (,HS and ,LS) and spin-transition spontaneous-strain (,) tensors. The eigendirections and eigenvalues of the , and , tensors correlate well with the weak and strong interactions in the solid and are responsible for the high cooperativity and low-dimensional behaviour. Magnetic and spectroscopic measurements were performed in all the different spin states and related to the structural findings. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Three-Dimensional Lanthanoid-Containing Coordination Frameworks: Structure, Magnetic and Fluorescent PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2005Hong-Tao Zhang Abstract Two lanthanoid-containing 3D coordination polymers, [Gd2L3(H2O)2]n (1) and {[TbL1.5(H2O)]·0.5H2O}n (2) (L = succinate), have been prepared by hydrothermal reaction. The difference in structure between the two 3D coordination polymers is a result of the flexibility of the ligand conformation. The magnetic properties of 1 and 2 have been investigated in the 1.8,300 K range. Both complexes exhibit ferromagnetic interaction between lanthanoid ions. AC magnetic measurements revealed long-range magnetic order in complex 2. Especially 2 integrates the ferromagnetic, fluorescent and porous properties into a single entity. This motif may be developed to achieve new multifunctional molecular-based materials. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Layered [BaM(C3H2O4)2(H2O)4] (M = Fe or Co) Complexes , Spectroscopic, Magnetic and Thermal StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2003Izaskun Gil de Muro Abstract Complexes with formula [BaM(C3H2O4)2(H2O)4], where M = Fe or Co, were synthesised and characterised. These two types of complexes are isostructural and crystallise in the Pccn space group. Their structure consists of two-dimensional networks of octahedral MO6 polyhedra in which the transition metal ions are coordinated by bridging malonate ligands, through the O-C-O atoms. These M-malonate units are extended along the crystallographic [101] plane. Spectroscopic data are consistent with the cations being in a high-spin octahedral symmetry. The two types of compounds exhibit 2D antiferromagnetic interactions as well as weak ferromagnetism below the Néel temperature, as a result of an intralayer misalignment of the spins. Thermal treatment of the metallo-organic precursors gave rise to BaMO3,y oxides at lower temperatures and reaction times than those found in the literature using the ceramic method. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003). [source] Magnetic, 57Fe Mössbauer, and IR Monitoring of the Thermal Spin Transition in a New Family of Iron(II) Spin-Transition ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2003Arno F. Stassen Abstract A new family of iron(II) tetrafluoroborate and perchlorate spin-crossover compounds has been synthesised and is discussed. The iron(II) ion is surrounded by six 1-ethyltetrazole ligands, which are halogen-substituted on the C2 atom of the ethyl group. The spin-crossover temperatures T1/2 are high compared to the unsubstituted (1-alkyltetrazole)iron(II) complexes. The shape of the spin-transition curve (i.e. ,HS vs. T) varies largely over the different complexes and appears to be influenced neither by the crystal packing, nor by the electronic effects. The temperature-dependent spin-transition behaviour has been studied by magnetic susceptibility and by 57Fe-Mössbauer spectroscopy. These data have been supported by temperature-dependent mid-range infrared spectroscopy: the thermally induced spin transition has been observed by direct monitoring of the aromatic C,H stretching frequency. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Multifunctional FeCo/TiN Multilayer Thin Films with Combined Magnetic and Protective Properties,ADVANCED ENGINEERING MATERIALS, Issue 12 2009Christian Klever Abstract Coatings with thicknesses ranging from a few nanometer up to several micrometer produced by physical vapor deposition (PVD) processes have been established in engineering technologies since the early 1980s. In particular, magnetron sputtered wear resistance coatings are industrially established and capable to enhance tool lifetimes significantly. However, in cases where optical inspection of a coating in use is not possible, an intrinsic sensor function of the film would be beneficial. Therefore, the development of wear resistant coatings with an integrated sensor functionality based on the insertion of a magnetoelastic ferromagnetic phase is suggested. In combination with appropriate read-out electronics such a film system would be ready for online monitoring of the coatings' actual state (e.g., strain, temperature, volume loss). This paper focuses on the development of wear resistance coatings which simultaneously supply beneficial mechanical properties as well as ferromagnetic properties optimized for online non-contact read-out applications. Multilayer coatings obtained through alternate stacking of magnetron sputtered TiN and FeCo layers with a nominal total thickness of 1000,nm were produced as a model system meeting the above conditions. The bilayer period was varied down to 2.6,nm while the individual layer thickness ratio tTiN/tFeCo was determined by the deposition rates and maintained constant at a value of about 3/1. The films were vacuum annealed ex situ in a static magnetic field subsequent to the deposition. The constitution of the as-deposited and annealed coatings as well as their mechanical (nanohardness, Young's modulus) and magnetic properties (magnetization hysteresis, frequency-dependent permeability) are described. Finally, the suitability of the coatings for the use in remote-interrogable wear sensor applications is briefly discussed. [source] Organic Ligands Made Porous: Magnetic and Catalytic Properties of Transition Metals Coordinated to the Surfaces of Mesoporous OrganosilicaADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Andreas Kuschel Abstract Inorganic solids with porosity on the mesoscale possess a high internal surface area and a well-accessible pore system. Therefore, it is a relevant task to equip the surfaces of such materials with a maximum density of various organic functional groups. Among these functions it is the capability of coordinating to metal species as a ligand that is of extraordinary importance in many areas, for example, in catalysis. This paper describes how prominent ligands containing donor functions such as carboxylic, thio, chelating, or amine groups can be obtained in the form of nanoporous organosilica materials. The coordination of metal centers such as CoII, MnII, VIV, or PtIV is studied in detail. The magnetic properties of the corresponding materials and some applications in catalysis are reported. A quantitative determination of the surface density of donor atoms by distance measurements using EPR spectroscopy is shown. [source] Synthesis of Magnetic, Up-Conversion Luminescent, and Mesoporous Core,Shell-Structured Nanocomposites as Drug CarriersADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Shili Gai Abstract The synthesis (by a facile two-step sol,gel process), characterization, and application in controlled drug release is reported for monodisperse core,shell-structured Fe3O4@nSiO2@mSiO2@NaYF4: Yb3+, Er3+/Tm3+ nanocomposites with mesoporous, up-conversion luminescent, and magnetic properties. The nanocomposites show typical ordered mesoporous characteristics and a monodisperse spherical morphology with narrow size distribution (around 80,nm). In addition, they exhibit high magnetization (38.0,emu g,1, thus it is possible for drug targeting under a foreign magnetic field) and unique up-conversion emission (green for Yb3+/Er3+ and blue for Yb3+/Tm3+) under 980,nm laser excitation even after loading with drug molecules. Drug release tests suggest that the multifunctional nanocomposites have a controlled drug release property. Interestingly, the up-conversion emission intensity of the multifunctional carrier increases with the released amount of model drug, thus allowing the release process to be monitored and tracked by the change of photoluminescence intensity. This composite can act as a multifunctional drug carrier system, which can realize the targeting and monitoring of drugs simultaneously. [source] Nanoshells with Targeted Simultaneous Enhancement of Magnetic and Optical Imaging and Photothermal Therapeutic ResponseADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Rizia Bardhan Abstract Integrating multiple functionalities into individual nanoscale complexes is of tremendous importance in biomedicine, expanding the capabilities of nanoscale structures to perform multiple parallel tasks. Here, the ability to enhance two different imaging technologies simultaneously,fluorescence optical imaging and magnetic resonance imaging,with antibody targeting and photothermal therapeutic actuation is combined all within the same nanoshell-based complex. The nanocomplexes are constructed by coating a gold nanoshell with a silica epilayer doped with Fe3O4 and the fluorophore ICG, which results in a high T2 relaxivity (390,mM,1,s,1) and 45× fluorescence enhancement of ICG. Bioconjugate nanocomplexes target HER2+ cells and induce photothermal cell death upon near-IR illumination. [source] Magnetic and Structural Investigation of ZnSe Semiconductor Nanoparticles Doped With Isolated and Core-Concentrated Mn2+ IonsADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Christina Graf X-Ray magnetic circular dichroism (XMCD) experiments on diluted magnetic semiconductor nanocrystals (2,7,nm) are reported in order to study their local electronic structure and magnetic properties. ZnSe nanoparticles containing either single manganese ions (Mn2+) distributed in the lattice of the entire particle or a MnSe core in the center are prepared using high temperature approaches. The Mn2+ concentration is varied between less than one to several tens of manganese ions per nanocrystal. For all samples it is shown that the Mn2+ is exclusively present in the bulk of ZnSe nanoparticles with no evidence for oxidation to higher Mn-oxidation states. The magnetic ions are highly polarized inside the nanocrystals reaching about 80% of the theoretical value of a pure d5 state under identical conditions for the case of isolated manganese ions. Nanocrystals with a MnSe core ZnSe shell structure reach <50% of this value. Thus, their polarization is significantly more hindered, which is due to the significantly enhanced Mn,Mn interactions and a more distorted crystalline lattice. In contrast, no coupling between the manganese centers is observed in the nanoparticles doped samples with low concentrations of Mn2+, indicating that these ions are isolated in the bulk of the nanoparticles. [source] Magnetic and viscous coupling at the core,mantle boundary: inferences from observations of the Earth's nutationsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2007B. A. Buffett SUMMARY Dissipative core,mantle coupling is evident in observations of the Earth's nutations, although the source of this coupling is uncertain. Magnetic coupling occurs when conducting materials on either side of the boundary move through a magnetic field. In order to explain the nutation observations with magnetic coupling, we must assume a high (metallic) conductivity on the mantle side of the boundary and a rms radial field of 0.69 mT. Much of this field occurs at short wavelengths, which cannot be observed directly at the surface. High levels of short-wavelength field impose demands on the power needed to regenerate the field through dynamo action in the core. We use a numerical dynamo model from the study of Christensen & Aubert (2006) to assess whether the required short-wavelength field is physically plausible. By scaling the numerical solution to a model with sufficient short-wavelength field, we obtain a total ohmic dissipation of 0.7,1 TW, which is within current uncertainties. Viscous coupling is another possible explanation for the nutation observations, although the effective viscosity required for this is 0.03 m2 s,1 or higher. Such high viscosities are commonly interpreted as an eddy viscosity. However, physical considerations and laboratory experiments limit the eddy viscosity to 10,4 m2 s,1, which suggests that viscous coupling can only explain a few percent of the dissipative torque between the core and the mantle. [source] Cover Picture: Composite Silica Spheres with Magnetic and Luminescent Functionalities (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 4 2006Mater. Abstract Photographs of a colloidal dispersion of composite nanoparticles with magnetic and luminescent functionalities are shown (left, in column), which are schematically illustrated in the main image. As reported by Salgueiriño-Maceira and co-workers on p.,509, such functionalities are imparted by magnetic and semiconductor nanoparticles within a silica matrix. In the absence of a magnetic field the particles are uniformly dispersed, although they accumulate and can be dragged under the influence of a magnetic field. Their movement can be monitored by their photoluminescence. A new class of highly fluorescent, photostable, and magnetic core/shell nanoparticles in the submicrometer size range has been synthesized from a modified Stöber method combined with the layer-by-layer (LbL) assembly technique. Luminescent magnetic nanoparticles are prepared via two main steps. The first step involves controlled addition of tetraethoxysilane to a dispersion of Fe3O4/,-Fe2O3 nanoparticles, which are thereby homogeneously incorporated as cores into monodisperse silica spheres. The second step involves the LbL assembly of polyelectrolytes and luminescent CdTe quantum dots onto the surfaces of the silica-coated magnetite/maghemite particles, which are finally covered with an outer shell of silica. These spherical particles have a typical diameter of 220,±,10,nm and a saturation magnetization of 1.34,emu,g,1 at room temperature, and exhibit strong excitonic photoluminescence. Nanoparticles with such a core/shell architecture have the added benefit of providing a robust platform (the outer silica shell) for incorporating diverse functionalities into a single nanoparticle. [source] Synthesis and Characterization of Dendrimeric Bridged Salen/Saloph Complexes and Investigation of Their Magnetic and Thermal BehaviorsHELVETICA CHIMICA ACTA, Issue 5 2010Ziya Erdem Abstract Eight new multinuclear FeIII and CrIII complexes involving the tetradentate Schiff bases N,N, -bis(salicylidene)ethylenediamine (salenH2) or N,N, -bis(salicylidene)benzene-1,2-diamine (salophH2) and the two new ligands 4,4,,4,,4,,,,4,,,,,4,,,,-[1,3,5-triazine-2,4,6-triyltris(nitrilomethylidyne-4,1-phenyleneoxy-1,3,5-triazine-6,2,4-triyldiimino)]hexakis[benzoic acid] (4) or 5,5,,5,,5,,,,5,,,,,5,,,,-[1,3,5-triazine-2,4,6-triyltris(nitrilomethylidyne-4,1-phenyleneoxy-1,3,5-triazine-6,2,4-triyldiimino)]hexakis[benzene-1,3-dicarboxylic acid] (5) were synthesized (Schemes,1 and 2) and characterized by means of 1H-NMR and FT-IR spectroscopy, elemental analysis, LC/MS analysis, AAS (atomic-absorption spectrum) analysis, thermal analyses, and magnetic-susceptibility measurements. The complexes can also be characterized as low-spin distorted-octahedral FeIII and CrIII complexes bridged by carboxylato moieties. [source] Magnetic and Electrical Characterizations of Half-Metallic Fe3O4 Nanowires,ADVANCED MATERIALS, Issue 17 2007M.-T. Chang The magnetic properties of magnetite (Fe3O4) nanowires are investigated by means of electron holography, which deduces the magnetic information from the phase shift of electrons. The magnetic flux is parallel to the longitudinal axis of the nanowires (see figure). Observations on the magnetization distribution reveal the possibility of regulating the spin current with the half-metallic nanowires, owing to the controlled magnetization distribution in the 1D form. [source] Magnetic activated cell sorting allows isolation of spermatogonia from adult primate testes and reveals distinct GFRa1-positive subpopulations in menJOURNAL OF MEDICAL PRIMATOLOGY, Issue 2 2010Kathrin Gassei Abstract Background, Isolation of spermatogonial stem cells (SSCs) could enable in vitro approaches for exploration of spermatogonial physiology and therapeutic approaches for fertility preservation. SSC isolation from adult testes is difficult due to low cell numbers and lacking cell surface markers. Glial cell-derived neurotrophic factor family receptor alpha-1 (GFR,1) plays a crucial role for the maintenance of SSCs in rodents and is expressed in monkey spermatogonia. Methods, Magnetic activated cell sorting was employed for the enrichment of GFR,1+ spermatogonia from adult primate testes. Results, Magnetic activated cell sorting of monkey cells enriched GFR,1+ cells threefold. 11.4% of GFR,1+ cells were recovered. 42.9% of GFR,1+ cells were recovered in sorted fractions of human testicular cells, representing a fivefold enrichment. Interestingly, a high degree of morphological heterogeneity among the GFR,1+ cells from human testes was observed. Conclusions, Magnetic activated cell sorting using anti-GFR,1 antibodies provides an enrichment strategy for spermatogonia from monkey and human testes. [source] Negative Thermal Expansion and Correlated Magnetic and Electrical Properties of Si-Doped Mn3GaN CompoundsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2010Ying Sun The negative thermal expansion (NTE) and correlated magnetic and electrical transport properties of Mn3GaxSi1,xN were investigated. For pure Mn3GaN, there is a large NTE effect corresponding to the antiferromagnetic to paramagnetic transition. Very interestingly, when partial Ga was replaced by Si, the NTE properties around the magnetic transition were changed. The NTE temperature range was broadened to ,T=148 K for Mn3Ga0.75Si0.25N and the linear thermal expansion coefficient was estimated as ,=,1.4 × 10,5 K,1 (272,420 K). Accordingly, the resistivity also showed a decrease from 327 to 395 K with temperature. With a further increasing Si content to x=0.5, the magnetic transition still occured, but the NTE effect did not appear. After careful observation, an anomaly was found at around 350 K in a,T, ,,T, and DSC curves of Mn3Ga0.5Si0.5N, respectively. This phenomenon strongly implies the close correlation among lattice, spin, and charge in this series materials. [source] Magnetic and Electrical Properties of (Mn, La)-Codoped SrTiO3 Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2008Song-Yin Zhang Mn-doped SrTiO3 -based thin films have been prepared by a simple sol,gel spin-coating method on silicon substrate. X-ray diffraction and high-resolution transmission electron microscopy reveal that these thin films are composed of amorphous and crystalline SrTiO3 phases. Optical and electrical measurements indicate that La codoping can make the band gap of SrTiO3 narrow and cause the leakage current to increase. Ferromagnetic behavior can be observed in these Mn- and/or La-codoped SrTiO3 -based thin films at room temperature, which should be ascribed to the magnetic coupling between the induced free electrons and Mn 3d spins. [source] Binding and Sulfonation of Poly(acrylic acid) on Iron Oxide Nanoparticles: a Novel, Magnetic, Strong Acid Cation Nano-AdsorbentMACROMOLECULAR RAPID COMMUNICATIONS, Issue 19 2005Sou-Yee Mak Abstract Summary: A novel, magnetic, strong acid cation nano-adsorbent has been developed by the covalent binding of poly(acrylic acid) on the surface of Fe3O4 nanoparticles followed by sulfonation using sulfanilic acid via carbodiimide activation. The nano-absorbent can be easily recovered or manipulated with an external magnetic field and shows a good capacity for the rapid and efficient adsorption of multivalent metal cations from aqueous solutions. An illustration for the binding and sulfonation of PAA on Fe3O4 nanoparticles to produce a magnetic, strong acid cation nano-adsorbent. [source] Magnetic characterization of Cretaceous-Tertiary boundary sedimentsMETEORITICS & PLANETARY SCIENCE, Issue 9 2007Víctor Villasante-Marcos Studied sections' locations vary in distance to the Chicxulub structure from distal (Agost and Caravaca, Spain), through closer (ODP Hole 1049A, Blake Nose, North Atlantic), to proximal (El Mimbral and La Lajilla, Mexico). A clear magnetic signature is associated with the fireball layer in the most distal sections, consisting of a sharp increase in susceptibility and saturation isothermal remanent magnetization (SIRM), and a decrease in remanence coercivity. Magnetic properties in these sections point to a distinctive ferrimagnetic phase, probably corresponding to the reported Mg- and Ni-rich, highly oxidized spinels of meteoritic origin. At closer and proximal sections magnetic properties are different. Although there is an increase in susceptibility and SIRM associated with a rusty layer placed on top of the siliciclastic deposit in proximal sections, and with a similar limonitic layer on top of the spherule bed that defines the boundary at Blake Nose, the magnetic properties indicate a mixture of iron oxyhydroxides dominated by fine-grained goethite. Based on previous geochemical studies at Blake Nose and new geochemical and PGE abundance measurements performed in this work at El Mimbral, this goethite-rich layer can be interpreted as an effect of diagenetic remobilization and precipitation of Fe. There is not enough evidence to assert that this Fe concentration layer at proximal sections is directly related to deposition of fine meteoritic material. Magnetic, geochemical, and iridium data reject it as a primary meteoritic phase. [source] Ternary magnetic nanocomposites based on core,shell Fe3O4/polyaniline nanoparticles distributed in PVDF matrixPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2010Mykhaylo Petrychuk Abstract Magnetic, electric, and radioprotector properties of hybrid nanocomposites of Fe3O4 nanoparticles with and without a shell of polyaniline (PANI), which is doped with dodecylbenzenesulfonic acid (DBSA), dispersed in polyvinylidene fluoride (PVDF) matrix have been studied. It has been found that the presence of PANI,DBSA as a separate filler in the ternary nanocomposite film, which also contains as another filler the core,shell Fe3O4/PANI,DBSA nanoparticles, facilitates dispersion of the magnetic filler due to the improvement of its compatibility with the PVDF matrix. This leads both to the decrease in coefficient of squareness of the hysteresis loop and to the increase in electromagnetic energy (EME) absorption of the nanocomposite film. [source] Magnetic and dielectric properties of the ruthenium double perovskites La2MRuO6 (M = Mg, Co, Ni, and Zn)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2006Kenji Yoshii Abstract Magnetic and dielectric properties of the ruthenium double perovskites La2MRuO6 (M = Mg, Co, Ni, and Zn) were investigated. The magnetization measurements for M = Co and Ni showed the existence of magnetic order at 20,30 K. Though the oxides with M = Zn and Mg exhibit a deviation from the Curie,Weiss law, magnetic order was not clearly observed. The result of La2ZnRuO6 was different from that previously reported, in which a ferromagnetic transition was found at around 165 K. The AC dielectric measurements for M = Co and Ni showed large dielectric constants (typically larger than 1000) at around room temperature, suggesting both the formation of short-ranged polar regions and the magnetic origin of large dielectric constant. In addition, two peaks were found for the temperature dependence of the tan , component for La2NiRuO6. The behavior suggests the existence of two different polar regions. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic and transport properties of the Co-doped manganite La0.7Sr0.3Mn1,xCoxO3 (0 , x , 0.5)PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2005B. C. Zhao Abstract The effect of Co doping on the magnetic and transport properties of La0.7Sr0.3Mn1,xCoxO3 (0 , x , 0.5) is investigated. The Co doping at Mn sites dilutes the double-exchange interaction between Mn3+ and Mn4+ ions and changes the long-range ferromagnetic (FM) order of La0.7Sr0.3MnO3 (LSMO) to the spin glass (SG) or cluster glass (CG) state for samples with x , 0.1. For x , 0.3, the paramagnetic (PM) metal to FM metal transition of LSMO disappears and the temperature dependence of resistivity ,(T) follows semiconducting behavior in the whole measured temperature region with the resistivity increasing by orders of magnitude. An interesting result is that ,(T) exhibits an obvious anomaly at T* , 100 K, which is ascribed to the spin-state transition of Co ions. For samples with x = 0.1 and 0.3, magnetoresistance (MR) effects are markedly enhanced in the low-temperature region compared with undoped LSMO, which is suggested to originate from the appearance of spin-dependent tunneling magnetoresistance. However, for samples with x = 0.5, the MR effect is suppressed over the entire temperature region measured and an obvious exchange anisotropy phenomenon, characterized by the shift of the hysteresis loop, is also observed, which is ascribed to the marked increase of the antiferromagnetic insulating phase. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Phase transitions in Sm1,xSrxMnO3 single crystals (0 , x , 0.8)PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003V. Yu. Abstract Magnetic and electrical properties of Sm1,xSrxMnO3 (0 , x , 0.8) single crystals have been studied and the T , x phase diagram has been revised. The compensation points of spontaneous weak ferromagnetic moment have been observed for pure SmMnO3 and for low doped compositions (0 , x < 0.05). For 0.4 , x , 0.475 the ferromagnetic ordering occurs as a first-order phase transition. It is shown that in a magnetic field the temperature of this transition increases and the transition becomes broader, which results in the appearance of a critical point (Tcr , 193 K, Hcr , 68 kOe for x = 0.45). Another transition, accompanied by a reduction of magnetization and noticeable anisotropy of magnetization curves, has been observed at low temperature Ts , 40 K. Below the Neel temperature, a pure antiferromagnetic state without spontaneous magnetization has been observed for 0.5 , x , 0.575, while for 0.6 , x , 0.675 an additional low-temperature transition to a new phase with a non-zero weak-ferromagnetic moment has been found. [source] Magnetic and electrical properties of BiMnO3 thin filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2007M. Grizalez Abstract BiMnO3 thin films were deposited on single-crystal (001)-oriented SrTiO3 substrates by rf-magnetron sputtering method. X-ray diffraction was used to analyze the crystal structure of the thin films, indicating that the films were monoclinic with two dominant orientation relationships along the substrate. The first is (111) BiMnO3 , (001) SrTiO3; the second is (222) BiMnO3 , (002) SrTiO3; other peaks showed that the films were polycrystalline. The roughness of the films was characterized by AFM. R vs. T was measured from 390 K to 15 K using a Keithley Model 167 Programmable Electrometer. Magnetic characterization was carried out by using a quantum designÔ magnetometer for magnetization versus temperature and for hysteresis loops at different temperatures. The saturation magnetic moment of 2.8,B per Mn ion (still fairly smaller than that of the bulk, 3.6,B) was observed at 5 K decreasing with increasing temperature. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic and electronic properties of transition metal nitride strained layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007M. Ribeiro Jr. Abstract We present a theoretical study with ab initio techniques on magnetic and electronic properties of 3d transition metal mononitrides. We perform the calculations in the wurtzite (w) and the zincblende (zb) structures, and find the tendency of all zb mononitrides to become half-metallic (HM) under hydrostatic strain. MnN, CrN, and VN become HM with integer magnetic moments of 4, 3 and 2,B, respectively. CrN shows ferromagnetism (FM) throughout the range of our lattice constant calculations, while VN is FM beyond the lattice constant of 4.65 Å. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic and XPS studies on TbNi5,xAlx systemPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004E. Burzo Abstract Magnetic measurements were performed on TbNi5,xAlx system, in the temperature range 1.7,300 K. At T = 1.7 K the saturation magnetizations are smaller than gJJ value of Tb. The nickel moments at 0 K, determined by band structure calculations are antiparallely oriented to Tb one and decrease in magnitude, being essentially null for TbNi3Al2 sample. The effective nickel moments vary from 2.10 ,B (x = 0) to , 1.10 ,B (x = 2). The XPS studies show that the Ni2p core level lines are similar to those of pure Ni, although the intensities of Ni 6 eV satellite decrease. The valence band spectra suggest an increase of the Ni3d,Al3p hybridization, when increasing Al content, in agreement with band structure calculations. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Multistep Continuous-Flow Microsynthesis of Magnetic and Fluorescent ,-Fe2O3@SiO2 Core/Shell Nanoparticles,ANGEWANDTE CHEMIE, Issue 39 2009Ali Abou-Hassan Dr. In gekoppelten Mikroreaktoren gelingt die schnelle, kontinuierliche Synthese der im Titel beschriebenen Nanopartikel: Im Mikroreaktor,I wird APTES aufgepfropft, in II werden sie mit den Sol-Gel-Vorstufen TEOS und Rhodamin-B-isothiocyanat(RITC)-markiertes APTES umgesetzt und in III beschichtet. Dieses Verfahren weist den Weg zu einer Lab-on-a-Chip-Synthese von Nanopartikeln. [source] Magnetic and seismic investigations of historic features in the Suchon area, Kongju, KoreaARCHAEOLOGICAL PROSPECTION, Issue 3 2008Jinyong Oh Abstract Integrated geophysical surveys including magnetometer, gradiometer and seismic refraction were performed in the Suchon area, Kongju, Korea, which revealed three locations of buried architectural features. The magnetometer survey identified four main anomalies that were further tested using the gradiometer. Application of the second vertical derivative and the high-pass filtering techniques to the magnetometer data isolated the deeper sources and enhanced the near-surface features. Depth was estimated using magnetometer data and seismic refraction analysis. The study identified three promising areas that are strongly recommended for excavation, which can be seen in the northeastern and southwestern parts of the study area. They are strongly linked to shallow historical features, i.e. brick tomb structure, pottery collection and stone-mound tomb, that were dominant during Baekche rule in Suchon area and therefore are believed to be from the Baekche period. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||||||||