Search results for "Magnetism"

Evidence for an African-Iberian mammal dispersal during the pre-evaporitic Messinian

2013

The accurate timing of biogeographic dispersal can be determined by examining the age of fossiliferous strata on either side of a physical barrier. Here we show that African mammals migrated to Iberia and European mammals migrated to North Africa at the same time before isolation of the Mediterranean Sea during the Messinian. The fossil site of Venta del Moro (Spain) exhibits western Europe’s most complete vertebrate fauna for the latest Miocene. Its uniquely cosmopolitan assemblage is evidence of faunal dispersals from Africa and Asia to Europe during the latest Miocene glaciation. A preliminary paleomagnetic study suggested an age of 5.8 Ma for this site, but our expanded magnetostratigra…

Distinct hematite populations from simultaneous fitting of Mössbauer spectra from Meridiani Planum, Mars

2010

[1] At Meridiani Planum, Mars, hematite occurs as a lag of ∼5 mm diameter spherules and their fragments and within the matrix of the sulfate-rich outcrop as <30 μm particles. Well crystalline and chemically pure bulk hematite undergoes a magnetic transition at ∼264 K (Morin transition) that can be detected by Mossbauer spectroscopy and is within the Martian diurnal temperature range. We analyzed outcrop and lag hematite Mossbauer spectra obtained by the Mars Exploration Rover (MER) Opportunity as a function of temperature using a simultaneous fitting procedure to determine the Morin temperature and the temperature interval over which it occurs. Mossbauer spectra for terrestrial hematite-bea…

Orientational dynamics of fluctuating dipolar particles assembled in a mesoscopic colloidal ribbon

2017

We combine experiments and theory to investigate the dynamics and orientational fluctuations of ferromagnetic microellipsoids that form a ribbonlike structure due to attractive dipolar forces. When assembled in the ribbon, the ellipsoids display orientational thermal fluctuations with an amplitude that can be controlled via application of an in-plane magnetic field. We use video microscopy to investigate the orientational dynamics in real time and space. Theoretical arguments are used to derive an analytical expression that describes how the distribution of the different angular configurations depends on the strength of the applied field. The experimental data are in good agreement with the…

Impact of graphitic carbon nitride nanosheets in mixed- matrix membranes for removal of heavy metals from water

2021

International audience; Removal of heavy metal ions from water is being a challenge and Polysulfone (PSf) membranes have shown great potential to remove them from contaminated solutions. In this work, the introduction of Graphitic carbon nitride nanosheets (g-C3N4) into PSf membranes was implemented to improve the permeability and separation performance of PSf membranes. g-C3N4 was incorporated into the membrane matrix via nonsolvent induced phase inversion method. The prepared mixed matrix membranes showed enhanced performances towards water filtration. The incorporation of g-C3N4 into the membrane matrix caused an increase in the desired physicochemical properties like hydrophilicity and …

Magnetic Excitations in Tetrameric Clusters of Polyoxometalates Observed by Inelastic Neutron Scattering. Evidence for Anisotropic Exchange Interacti…

1997

Magnetic excitations in tetranuclear clusters of exchange-coupled metal ions encapsulated by polyoxotungstate ligands (1) have been observed by inelastic neutron scattering (INS) in the salts K10[M4(H2O)2(PW9O34)2]·nH2O, where M2+ = Mn, Co, and Ni. INS provides a much deeper and more detailed insight into the nature of the magnetic coupling in these clusters than bulk techniques. In particular, anisotropic exchange interactions are evidenced in the ferromagnetic Co4 cluster.

Oligo-m-phenyleneoxalamide Copper(II) Mesocates as Electro-Switchable Ferromagnetic Metal–Organic Wires

2010

Double-stranded copper(II) string complexes of varying nuclearity, from di- to tetranuclear species, have been prepared by the CuII-mediated self-assembly of a novel family of linear homo- and heteropolytopic ligands that contain two outer oxamato and either zero (1 b), one (2 b), or two (3 b) inner oxamidato donor groups separated by rigid 2-methyl-1,3-phenylene spacers. The X-ray crystal structures of these CuIIn complexes (n=2 (1 d), 3 (2 d), and 4 (3 d)) show a linear array of metal atoms with an overall twisted coordination geometry for both the outer CuN2O2 and inner CuN4 chromophores. Two such nonplanar all-syn bridging ligands 1 b–3 b in an anti arrangement clamp around the metal ce…

Inside Cover: Oligo-m-phenyleneoxalamide Copper(II) Mesocates as Electro-Switchable Ferromagnetic Metal-Organic Wires (Chem. Eur. J. 43/2010)

2010

The half-metallic ferromagnet

2007

Abstract Electronic structure calculation were used to predict a new material for spintronic applications. Co 2 Mn 0.5 Fe 0.5 Si is one example which is stable against on-site correlation and disorder effects due to the position of the Fermi energy in the middle of the minority band gap. Experimentally the sample were made exhibiting L 2 1 structure and a high magnetic order.

Design of Low-Dimensional Ferrimagnetic Compounds: New Magnetic Lattices in the “EDTA-Family”

1987

The ability of EDTA to wrap around one metal atom (M′) while still providing bridging carboxylate groups to a second atom (M) is the basis for the obtainment of a wide variety of low-dimensional bimetallic ordered systems.

Structural and Magnetic Insights into the Trinuclear Ferrocenophane and Unexpected Hydrido Inverse Crown Products of Alkali‐Metal‐Mediated Manganatio…

2008

With the aim of introducing the diisopropylamide [NiPr(2)](-) ligand to alkali-metal-mediated manganation (AMMMn) chemistry, the temperature-dependent reactions of a 1:1:3 mixture of butylsodium, bis(trimethylsilylmethyl)manganese(II), and diisopropylamine with ferrocene in hexane/toluene have been investigated. Performed at reflux temperature, the reaction affords the surprising, ferrocene-free, hydrido product [Na(2)Mn(2) (mu-H)(2){N(iPr)(2)}(4)]2 toluene (1), the first Mn hydrido inverse crown complex. Repeating the reaction rationally, excluding ferrocene, produces 1 in an isolated crystalline yield of 62 %. At lower temperatures, the same bimetallic amide mixture leads to the manganati…