Surface Adsorption Mechanism between Lead(II,IV) and Nanomaghemite Studied on Polluted Water Samples Collected from the Peruvian Rivers Mantaro and Cumbaza.

Real water remediation is an important issue that requires the development of novel adsorbents with remarkable adsorption properties, permitting reusability. In this work, the surface and adsorption properties of bare magnetic iron oxide nanoparticles were systematically studied, before and after the application of a maghemite nanoadsorbent in two real Peruvian effluents severely contaminated with Pb(II), Pb(IV), Fe(III), and others. We were able to describe the Fe and Pb adsorption mechanisms that occurred at the particle surface.

Progress toward Room-Temperature Synthesis and Functionalization of Iron-Oxide Nanoparticles.

Novel magnetic nanohybrids composed of nanomaghemite covered by organic molecules were successfully synthesized at room temperature with different functionalization agents (sodium polystyrene sulfonate, oxalic acid, and cetyltrimethylammonium bromide) in low and high concentrations. Structural, vibrational, morphological, electron energy-loss spectroscopy, magnetic, and Mössbauer characterizations unraveled the presence of mainly cubic inverse spinel maghemite (γ-FeO), whilst X-ray diffraction and Fe Mössbauer spectroscopy showed that most samples contain a minor amount of goethite phase (α-FeOOH). Raman analysis at different laser power revealed a threshold value of 0.

Magnetic Simulations of Core-Shell Ferromagnetic Bi-Magnetic Nanoparticles: The Influence of Antiferromagnetic Interfacial Exchange.

Magnetic properties of ferromagnetic nanostructures were studied by atomistic simulations following Monte Carlo and Landau-Lifshitz-Gilbert approaches. First, we investigated the influence of particle size and shape on the temperature dependence of magnetization for single cobalt and gadolinium nanoparticles and also in bi-magnetic Co@Gd core-shell nanoparticles with different sizes. The Landau-Lifshitz-Gilbert approach was subsequently applied for inspecting the magnetic hysteresis behavior of 2 and 4 nm Co@Gd core-shell nanoparticles with negative, positive, and zero values of interfacial magnetic exchange.

Improved Removal Capacity and Equilibrium Time of Maghemite Nanoparticles Growth in Zeolite Type 5A for Pb(II) Adsorption.

Novel magnetic zeolite type 5A nanocomposites were synthesized by the co-precipitation method and applied to lead removal from aqueous ambient. Maghemite nanoparticles were mixed with zeolite and, by controlling its content, transmission electron microscopy results gave sizes of 5 to 15 nm and selected area electron diffraction patterns confirmed the presence of zeolite. The nanocomposites have high specific surface area with values up to 194 m/g.

Shell-mediated control of surface chemistry of highly stoichiometric magnetite nanoparticles.

Magnetite (Fe3O4) nanoparticles are one of the most studied nanomaterials for different nanotechnological and biomedical applications. However, Fe3O4 nanomaterials gradually oxidize to maghemite (γ-Fe2O3) under conventional environmental conditions leading to changes in their functional properties that determine their performance in many applications. Here we propose a novel strategy to control the surface chemistry of monodisperse 12 nm magnetite nanoparticles by means of a 3 nm-thick Zn-ferrite epitaxial coating in core/shell nanostructures.

Fe Deficiencies, FeO Subdomains, and Structural Defects Favor Magnetic Hyperthermia Performance of Iron Oxide Nanocubes into Intracellular Environment.

Herein, by studying a stepwise phase transformation of 23 nm FeO-FeO core-shell nanocubes into FeO, we identify a composition at which the magnetic heating performance of the nanocubes is not affected by the medium viscosity and aggregation. Structural and magnetic characterizations reveal the transformation of the FeO-FeO nanocubes from having stoichiometric phase compositions into Fe-deficient FeO phases. The resultant nanocubes contain tiny compressed and randomly distributed FeO subdomains as well as structural defects.

Manipulating the morphology of the nano oxide domain in AuCu-iron oxide dumbbell-like nanocomposites as a tool to modify magnetic properties.

We report the colloidal synthesis of hybrid dumbbell-like nanocrystals (NCs) which feature a plasmonic metal domain (M) attached to a morphologically-tunable magnetic oxide domain (MOx). We highlight how the modulation of the amount of oleic acid (OlAc) in the synthesis mixture influences the final composition of the M domain, the morphology of the MOx domain and, consequently, the magnetic properties of the hetero-structures. In the presence of high amounts of OlAc, a crystalline, magnetite MOx is mainly formed, coupled with a partial dealloying between Au and Cu in the M domain.

Spin-liquid-like state in a spin-1/2 square-lattice antiferromagnet perovskite induced by d-d cation mixing.

A quantum spin liquid state has long been predicted to arise in spin-1/2 Heisenberg square-lattice antiferromagnets at the boundary region between Néel (nearest-neighbor interaction dominates) and columnar (next-nearest-neighbor interaction dominates) antiferromagnetic order. However, there are no known compounds in this region. Here we use d-d cation mixing to tune the magnetic interactions on the square lattice while simultaneously introducing disorder.

Size dependent structural and magnetic properties of FeO-Fe3O4 nanoparticles.

The magnetic properties of monodisperse FeO-Fe3O4 nanoparticles with different mean sizes and volume fractions of FeO synthesized via decomposition of iron oleate were correlated to their crystallographic and phase compositional features by exploiting high resolution transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy and field and zero field cooled magnetization measurements. A model describing the phase transformation from a pure Fe3O4 phase to a mixture of Fe3O4, FeO and interfacial FeO-Fe3O4 phases as the particle size increases was established. The reduced magnetic moment in FeO-Fe3O4 nanoparticles was attributed to the presence of differently oriented Fe3O4 crystalline domains in the outer layers and paramagnetic FeO phase.

Highly stable monodisperse PEGylated iron oxide nanoparticle aqueous suspensions: a nontoxic tracer for homogeneous magnetic bioassays.

Uniformly sized and shaped iron oxide nanoparticles with a mean size of 25 nm were synthesized via decomposition of iron-oleate. High resolution transmission electron microscopy and Mössbauer spectroscopy investigations revealed that the particles are spheres primarily composed of Fe3O4 with a small fraction of FeO. From Mössbauer and static magnetization measurements, it was deduced that the particles are superparamagnetic at room temperature.

Magnetism of the chromium thio-spinels Fe1-xCuxCr2S4 studied using muon spin rotation and relaxation.

Powder samples of Fe1-xCuxCr2S4 with x = 0,0.2,0.5,0.

Low temperature incommensurately modulated and noncollinear spin structure in FeCr2S4.

FeCr(2)S(4) orders magnetically at T(N)≈ 170 K. According to neutron diffraction, the ordered state down to 4.2 K is a simple collinear ferrimagnet maintaining the cubic spinel structure.

Field-induced coupled superconductivity and spin density wave order in the heavy fermion compound CeCoIn5.

The high-field superconducting state in CeCoIn(5) has been studied by transverse field muon spin rotation measurements with an applied field parallel to the crystallographic c axis close to the upper critical field mu(0)H(c2) = 4.97 T. At magnetic fields mu(0)H > or = 4.

Oxidation states of Co and Fe in Ba(1-x)Sr(x)Co(1-y)Fe(y)O(3-delta) (x, y = 0.2-0.8) and oxygen desorption in the temperature range 300-1273 K.

Four compositions of Ba(1-x)Sr(x)Co(1-y)Fe(y)O(3-delta) were studied for phase, oxygen uptake-release, and transition metal (TM) oxidation states after solid state processing and with in situ heating from 300 to 1273 K in air. X-Ray diffraction showed that all compositions except one had the cubic perovskite structure at all temperatures; that with x, y = 0.2 was a mixture as prepared, becoming predominantly cubic at high temperature.

The electronic phase diagram of the LaO(1-x)F(x)FeAs superconductor.

The competition of magnetic order and superconductivity is a key element in the physics of all unconventional superconductors, for example in high-transition-temperature cuprates, heavy fermions and organic superconductors. Here superconductivity is often found close to a quantum critical point where long-range antiferromagnetic order is gradually suppressed as a function of a control parameter, for example charge-carrier doping or pressure. It is believed that dynamic spin fluctuations associated with this quantum critical behaviour are crucial for the mechanism of superconductivity.

Commensurate spin density wave in LaFeAsO: a local probe study.

We present a detailed study on the magnetic order in the undoped mother compound LaFeAsO of the recently discovered Fe-based superconductor LaFeAsO1-xFx. In particular, we present local probe measurements of the magnetic properties of LaFeAsO by means of 57Fe Mössbauer spectroscopy and muon-spin relaxation in zero external field along with magnetization and resistivity studies. These experiments prove a commensurate static magnetic order with a strongly reduced ordered moment of 0.

Giant spin canting in the S=1/2 antiferromagnetic chain [CuPM(NO3)2(H2O)2]n observed by 13C-NMR.

We present a combined experimental and theoretical study on copper pyrimidine dinitrate [CuPM(NO3)2(H2O)2]n, a one-dimensional S=1/2 antiferromagnet with alternating local symmetry. From the local susceptibility measured by NMR at the three inequivalent carbon sites in the pyrimidine molecule we deduce a giant spin canting, i.e.

Metallic ground state and glassy transport in single crystalline URh2Ge2: enhancement of disorder effects in a strongly correlated electron system.

We present a detailed study of the electronic transport properties on a single crystalline specimen of the moderately disordered heavy-fermion system URh2Ge2. For this material, we find glassy electronic transport in a single crystalline compound. We derive the temperature dependence of the electrical conductivity and establish metallicity by means of optical conductivity and Hall effect measurements.

Observation of the conduction electron spin polarization in the Ag spacer of a Fe/Fg/Fe trilayer.

The spatially oscillating electron spin polarization in the Ag spacer of a 4 nm Fe/20 nmAg/4 nm Fe(001) epitaxial trilayer has been determined by means of low energy muon spin rotation. It oscillates with the same period as the interlayer exchange coupling, but shows a much weaker attenuation at large distances x from the interface. The measured magnetization profile from the inner 14 nm of the spacer is described by an oscillating polarization decaying as x(-0.

From antiferromagnetic order to static magnetic stripes: the phase diagram of (La,Eu)2-xSrxCuO4.

The magnetic order of (La,Eu)2-xSrxCuO4 ( x View Article and Find Full Text PDF