Mapping the magnetic coupling of self-assembled Fe3O4 nanocubes by electron holography

The nanoscale magnetic configuration of self-assembled groups of magnetite 40 nm cubic nanoparticles has been investigated by means of electron holography in the transmission electron microscope (TEM). The arrangement of the cubes in the form of chains driven by the alignment of their dipoles of single nanocubes is assessed by the measured in-plane magnetic induction maps, in good agreement with theoretical calculations

Thermal, dielectrical and mechanical response of α and β-poly(vinilydene fluoride)/Co-MgO nanocomposites

Nanocomposites of the self-forming core-shell Co-MgO nanoparticles, which were of approximately 100 nm in diameter, and poly(vinylidene fluoride) (PVDF) polymer have been prepared. When the polymer is crystallized in the α-phase, the introduction of the nanoparticles leads to nucleation of the γ-phase of PVDF, increasing also the melting temperature of the polymer. With the introduction of the Co-MgO particles, the dielectric constant of the material slightly increases and the storage modulus decreases with respect to the values obtained for the pure polymer

Enhanced and oscillatory magnetoresistance of thin Fe(001) films

We have studied the magnetoresistance of single-crystalline (001) Fe films prepared by sputtering techniques and covered by epitaxial MgO or Pt protective layers. The influence of the thickness of the magnetic layer as well as of the nature of the capping layer on the Fe anisotropic magnetoresistance was investigated by four-terminal probe, measurements performed with the current J in the [110] magnetically hard direction. We found an enhancement in the magnetoresistance value with respect to bulk and oscillations in the high field regime in MgO covered Fe/MgO(001) ultrathin films. A plausible explanation is that the enhanced magnetoresistance is due to electronic confinement effects, not present in similar Pt/Fe/MgO(001) samples.The authors acknowledge Dr. F. Aliev for fruitful discussions and the Spanish Commission of Science and Technology for financial support. One of the authors (Ll.B.) acknowledges support through Project No. MAT2003-04161.Peer reviewe

Spatial and chemical interface asymmetry in Fe/MgO/Fe(001) heterostructures

F. J. Palomares and C. Munuera Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049 Madrid, Spain C. Martínez Boubeta and A. Cebollada Instituto de Microelectrónica de Madrid IMM (CNM-CSIC), Isaac Newton 8, P.T.M. 28760 Madrid, Spain The chemical nature of the different interfaces and possible segregation effects are studied in fully epitaxial Fe/MgO/Fe (001) oriented heterostructures fabricated by combined sputtering plus laser ablation deposition techniques. Auger electron spectroscopy depth profiling experiments showed that the interfaces of the MgO spacer with the Fe layers are different, the inner MgO/Fe being spatially broader and with an FeO interlayer, while that of the outer Fe/MgO is spatially narrower with no evidence of FeO formation. This spatial and chemical asymmetry is interpreted in terms of the different deposition procedures, which affect the formation of both interfaces. No Fe segregation in the MgO layers or MgO segregation in the Fe films is observed.This work was supported by the Spanish MCyT.Peer reviewe

Interfacial geometry dependence of the iron magnetic moment: the case of MgO/Fe/MgO

The prediction and experimental demonstration of a very large magnetoresistance in Fe/MgO/Fe tunnel junctions have led to intense study of related systems in the last decade. In the present paper, we concentrate on the role of interface coordination, Fe thickness, and magnetization in the MgO/Fe/MgO mirror. By first-principles analysis, it is shown that the iron magnetic moment can rise up to 4 μB, accounting for observed deviation of the Fe atoms in the vicinity of MgO interfaces. The origin is attributed to site preference predicted by our calculations, namely, that, unlike the case of Fe atoms in the monolayer range sitting just above the oxygen atoms of the MgO(001) substrate, the charge transfer induced by the O p-d Fe interaction leads to a structural distortion that stabilizes the Mg at the very first deposition stages of the capping layer, facing Fe sites

A core-shell composition for purifying contaminated water and/or biological-medical systems such as tissues, cells or blood

[ES] Una composición de núcleo-corteza para purificar agua contaminada y/o sistemas biológicos-médicos como tejidos, células o sangre. La invención se refiere a una composición de núcleo-corteza que comprende un núcleo de nanopartículas magnéticas y una corteza de un compuesto de hidróxido doble laminar, y su procedimiento de obtención. Asimismo, la invención se refiere al uso de dicha composición para purificar agua contaminada, especialmente útil para la retirada de contaminantes nocivos como arsénico, para hacer el agua adecuada para el consumo humano. Además, la invención se refiere al uso de dicha composición para purificar sistemas biológicos-médicos como tejidos, células o sangre.[EN] The invention relates to core-shell composition comprising a core of magnetic nanoparticles and a shell of a layered double hydroxide compound, and its procedure of obtainment. Furthermore, the invention refers to the use of said composition for purifying contaminated water, especially useful for the removal of harmful contaminants like arsenic, to make the water suitable for human consumption. Moreover, the invention refers to the use of said composition for purifying biological-medical systems such as tissues, cells or blood.Peer reviewedConsejo Superior de Investigaciones Científicas (España)A1 Solicitud de patente con informe sobre el estado de la técnic

A core-shell composition for purifying contaminated water and/or biological-medical systems such as tissues, cells or blood

[ES] Una composición de núcleo-corteza para purificar agua contaminada y/o sistemas biológicos-médicos como tejidos, células o sangre. La invención se refiere a una composición de núcleo-corteza que comprende un núcleo de nanopartículas magnéticas y una corteza de un compuesto de hidróxido doble laminar, y su procedimiento de obtención. Asimismo, la invención se refiere al uso de dicha composición para purificar agua contaminada, especialmente útil para la retirada de contaminantes nocivos como arsénico, para hacer el agua adecuada para el consumo humano. Además, la invención se refiere al uso de dicha composición para purificar sistemas biológicos-médicos como tejidos, células o sangre.[EN] The invention relates to core-shell composition comprising a core of magnetic nanoparticles and a shell of a layered double hydroxide compound, and its procedure of obtainment. Furthermore, the invention refers to the use of said composition for purifying contaminated water, especially useful for the removal of harmful contaminants like arsenic, to make the water suitable for human consumption. Moreover, the invention refers to the use of said composition for purifying biological-medical systems such as tissues, cells or blood.Peer reviewedConsejo Superior de Investigaciones Científicas (España)B1 Patente sin examen previ

Linear and quadratic magneto-optical Kerr effects in continuous and granular ultrathin monocrystalline Fe films

The effects of nanostructuration on the magneto-optic properties of ultrathin monocrystalline iron films grown on MgO (001) are investigated through the magneto-optic coefficients, which have a linear and quadratic dependence on the magnetization. The photon energy dependence of such magneto-optic coefficients is determined by measuring the relative variations of the reflectivity (ΔRpp/Rpp) for p-polarized incident and reflected light (p-p polarized) when the magnetization rotates in the plane of the sample. Thick Fe films present a magneto-optical anisotropy, which has a quadratic dependence on the magnetization. Such anisotropy is strongly reduced in nanostructured iron thin films formed by nanometric iron islands. The modifications induced by the nanostructuration are stronger for the magneto-optical coefficients, which have a quadratic dependence on the magnetization in contrast to the linear terms. A self-consistent effective-medium formalism is presented that explains the modifications induced in the magneto-optical coefficients by nanostructuration.Peer reviewe

Una composición de núcleo-corteza para purificar agua contaminada y/o sistemas biológicos-médicos como tejidos, células o sangre

[EN] The invention relates to core-shell composition comprising a core of magnetic nanoparticles and a shell of a layered double hydroxide compound, and its procedure of obtainment. Furthermore, the invention refers to the use of said composition for purifying contaminated water, especially useful for the removal of harmful contaminants like arsenic, to make the water suitable for human consumption. Moreover, the invention refers to the use of said composition for purifying biological-medical systems such as tissues, cells or blood.[ES] Una composición de núcleo-corteza para purificar agua contaminada y/o sistemas biológicos-médicos como tejidos, células o sangre. La invención se refiere a una composición de núcleo-corteza que comprende un núcleo de nanopartículas magnéticas y una corteza de un compuesto de hidróxido doble laminar, y su procedimiento de obtención. Asimismo, la invención se refiere al uso de dicha composición para purificar agua contaminada, especialmente útil para la retirada de contaminantes nocivos como arsénico, para hacer el agua adecuada para el consumo humano. Además, la invención se refiere al uso de dicha composición para purificar sistemas biológicos-médicos como tejidos, células o sangre.Peer reviewedConsejo Superior de Investigaciones Científicas (España)B1 Patente sin examen previ

Magneto-optical light scattering from ferromagnetic surfaces

We have studied the optical and magneto-optical components of the light scattered by the surface of several Fe films with different morphologies. We present a method, based on the ratio between the optical and magneto-optical components of the scattered intensity, to discern the physical origin, either structural or magnetic corrugation, of the light scattered by these ferromagnetic surfaces. Surface versus bulk magnetic information can be separated by magneto-optical light scattering measurements, the scattered light being more sensitive to magnetization differences between surface and bulk than the reflected one.This work was performed under Spanish CICyT financial support. One of the authors (M.U.G.) thanks the Consejería de Educación y Cultura de la Comunidad de Madrid for funding. One of the authors (C.M.B.) acknowledges a grant from the Ministerio de Ciencia y Tecnología.Peer reviewe