scholarly journals Tunable magnetism on the lateral mesoscale by post-processing of Co/Pt heterostructures

2015 ◽  
Vol 6 ◽  
pp. 1082-1090 ◽  
Author(s):  
Oleksandr V Dobrovolskiy ◽  
Maksym Kompaniiets ◽  
Roland Sachser ◽  
Fabrizio Porrati ◽  
Christian Gspan ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Behavior ◽  
Basic Research ◽  
Post Processing ◽  
Transmission Electron ◽  
Spin Dependent Transport ◽  
Complementary Approach ◽  
Dependent Transport ◽  
High Degree

Controlling magnetic properties on the nanometer-scale is essential for basic research in micro-magnetism and spin-dependent transport, as well as for various applications such as magnetic recording, imaging and sensing. This has been accomplished to a very high degree by means of layered heterostructures in the vertical dimension. Here we present a complementary approach that allows for a controlled tuning of the magnetic properties of Co/Pt heterostructures on the lateral mesoscale. By means of in situ post-processing of Pt- and Co-based nano-stripes prepared by focused electron beam induced deposition (FEBID) we are able to locally tune their coercive field and remanent magnetization. Whereas single Co-FEBID nano-stripes show no hysteresis, we find hard-magnetic behavior for post-processed Co/Pt nano-stripes with coercive fields up to 850 Oe. We attribute the observed effects to the locally controlled formation of the CoPt L10 phase, whose presence has been revealed by transmission electron microscopy.

Reversal Mechanisms in Lithographically Defined Magnetic Thin Film Elements Imaged by Scanning Transmission Electron Microscopy

1997 ◽  
Vol 3 (2) ◽  
pp. 146-153 ◽  
Author(s):  
Stephen McVitie ◽  
John N. Chapman
Keyword(s):  
Thin Film ◽  
Scanning Transmission Electron Microscopy ◽  
Magnetic Behavior ◽  
Hysteresis Cycle ◽  
Magnetic Thin Film ◽  
Lorentz Microscopy ◽  
Magnetic Imaging ◽  
Transmission Electron ◽  
Scanning Transmission

Abstract: The magnetic behavior of lithographically defined thin film elements of permalloy imaged by Lorentz microscopy is described. Elements of thickness <100 nm, with in-plane dimensions in the micron and sub-micron range and of varying shape, have been subjected to in situ fields using an electron microscope that has been optimized for magnetic imaging. The information provided from the imaging modes has identified the details of the magnetization reversal mechanisms in the elements during the course of a hysteresis cycle. In particular, domain wall clusters which form at the edges of the elements are observed prior to switching of the magnetization. Results are described from elements with near single and multidomain structures with different geometry.

Iron Oxide Nanoparticles Obtained from a Fe(II) - Chitosan Polymer Film

2010 ◽  
Vol 644 ◽  
pp. 51-55 ◽  
Author(s):  
Juan Fco Luna Martínez ◽  
E. Reyes-Melo ◽  
Virgilio González-González ◽  
A. Torres-Castro ◽  
Carlos Guerrero-Salazar ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Composite Film ◽  
Polymer Film ◽  
Iron Oxide Nanoparticles ◽  
Magnetic Behavior ◽  
Nanostructured Material ◽  
Oxide Nanoparticles ◽  
Transmission Electron ◽  
Alkaline Conditions

In this work, iron oxide nanoparticles (~5 nm) embedded in a chitosan polymer film, were synthesized. In order to obtain this nanostructured material, firstly a homogenous film of Fe(II)-chitosan was prepared. The resulting composite film has a thickness of ~140μm. Iron oxide nanoparticles were in-situ synthesized by treating the composite film with H2O2 under alkaline conditions. The morphological analysis by Transmission Electron Microscopy (TEM) shows the nanoparticles were embedded and stabilized in chitosan polymer film. The magnetic behavior was studied by magnetization measurements. The magnetization curves at room temperature showed that iron oxide nanoparticles have a superparamagnetic behavior.

In Situ Analysis of magnetic and Structural Properties of Epitaxial and Polycrystalline Ni80Fe20 Thin Films

1993 ◽  
Vol 313 ◽  
Author(s):  
I. Hashim ◽  
H.A. Atwater ◽  
Thomas J. Watson
Keyword(s):  
Magnetic Properties ◽  
Kerr Effect ◽  
High Energy ◽  
Epitaxial Films ◽  
Interface Roughness ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Transmission Electron

ABSTRACTWe have investigated structural and magnetic properties of epitaxial Ni80Fe20 films grown on relaxed epitaxial Cu/Si (001) films. The crystallographic texture of these films was analyzed in situ by reflection high energy electron diffraction (RHEED), and ex situ by x-ray diffraction and cross-sectional transmission electron Microscopy (XTEM). In particular, RHEED intensities were recorded during epitaxial growth, and intensity profiles across Bragg rods were used to calculate the surface lattice constant, and hence, find the critical epitaxial thickness for which Ni80Fe20 grows pseudomorphically on Cu (100). XTEM analysis indicated that the epitaxial films had atomically-abrupt interfaces which was not the case for polycrystalline Cu and Ni80Fe20 film interfaces. The Magnetic properties of these epitaxial films were Measured in situ using Magneto-optic Kerr effect magnetometry and were compared with those of polycrystalline films grown on SiO2/Si. Large Hc (∼ 35 Oe) was observed for epitaxial Ni80Fe20 films less than 3.0 nm thick whereas for increasing thickness, Hc decreased approximately monotonically to a few Oersteds. Correlations were made between magnetic properties of these epitaxial films, the strain in the film and the interface roughness obtained from XTEM analysis.

scholarly journals Technology for obtaining modified oil sorbents

2021 ◽  
Vol 82 (4) ◽  
pp. 247-253
Author(s):  
R. Mejri ◽  
Y. S. Peregudov ◽  
E. M. Gorbunova
Keyword(s):  
Magnetic Properties ◽  
High Efficiency ◽  
Low Cost ◽  
Oil Products ◽  
Solid Surfaces ◽  
Environmental Friendliness ◽  
Transmission Electron ◽  
Oil Sorbent ◽  
High Degree ◽  
Oil And Oil Products

Expediency of using natural glauconite material as a basis for the production of an environmentally friendly sorbent with hydrophobic and magnetic properties for liquidating oil and oil products spills mechanically and using a magnetic field has been substantiated and experimentally proved. Fractional, elemental and oxide compositions of the original mineral have been studied. The structure of glauconite fraction 0.045-0.1 mm has been investigated by transmission electron microscopy. It was found that the surface of the sample particles is heterogeneous with a large number of pores and cracks. Based on the experimental data, the optimal conditions for the production and use of powder and granular sorbents based on glauconite with specified properties were determined, at which a high degree of recovery (more than 90%) of oil with water and hard surfaces. The optimum temperature for obtaining a magnetic oil sorbent is 400 °C. The doses of stearic acid and iron (III) oxide were established at 5 wt. %, which provide hydrophobicity and magnetic properties to the synthesized sorbent. A high degree of oil (97%) and oil (98%) recovery when using a sorbent is achieved at a ratio of 1: 10 to sorbate. To eliminate oil and oil product spills, it is proposed to use granular ferromagnetic sorbents obtained by introducing carboxymethyl cellulose into the modified glauconite composition. oil and oil products granular sorbent increases in comparison with the original mineral by 1.2–2.2 times. Technological schemes for obtaining ferromagnetic hydrophobic and granular sorbents based on glauconite for collecting oil and oil products from water and solid surfaces have been developed. The synthesized sorbents are characterized by high efficiency, low cost, and environmental friendliness.

Magnetic Properties of γ-Fe2O3/Poly(Ether-Ester) Nanocomposites

2008 ◽  
Vol 8 (4) ◽  
pp. 2127-2134 ◽  
Author(s):  
N. Guskos ◽  
V. Likodimos ◽  
S. Glenis ◽  
M. Maryniak ◽  
M. Baran ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Nanoparticles ◽  
Magnetic Behavior ◽  
Thermoplastic Elastomer ◽  
Relaxation Processes ◽  
Close Correspondence ◽  
Polycondensation Reaction ◽  
Dispersion State ◽  
Ether Ester

The magnetic properties of γ-Fe2O3 nanoparticles embedded in a thermoplastic elastomer poly(ether-ester) copolymer by the in situ polycondensation reaction process have been investigated by means of magnetization and ferromagnetic resonance (FMR) measurements at low filler concentrations of 0.1 and 0.3 wt% with the magnetic additive introduced in the polymer matrix in powder and solution form. The magnetic behavior of the magnetopolymeric nanocomposites indicates significant interparticle interaction effects that depend mainly on the dispersion state of the magnetic nanoparticles as well as their concentration, consistent with the variation of the particle microstructure characterized by magnetic aggregates in the nanometer and micron scale for the solution and powder dispersions, respectively. The magnetization and FMR results at different filler concentrations and dispersions showa close correspondence to the relaxation processes of the copolymer, implying the coupling of polymeric and magnetic properties.

Mössbauer and magnetization studies of mechanically milled nanocrystalline Fe1–xAlx alloys

2015 ◽  
Vol 93 (11) ◽  
pp. 1257-1263
Author(s):  
S. Rajan ◽  
R. Shukla ◽  
A. Kumar ◽  
A. Vyas ◽  
S. Khan ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Behavior ◽  
High Energy ◽  
Milling Process ◽  
Transmission Electron ◽  
Bulk Magnetization ◽  
Hyperfine Field Distributions ◽  
Equilibrium Process ◽  
Energy Ball ◽  
Evolution Of Microstructure

Changes in the magnetic behavior of Fe1–xAlx (x = 0.3, 0.4, 0.5, 0.6) powders during mechanical alloying have been studied. The ball milling process leads to formation of solid state reaction assisted by severe plastic deformation because of which crystallite size is reduced and as a result of which interesting magnetic properties are developed. The evolution of magnetic order in high-energy ball-milled Fe–Al solid solution is investigated using 57Fe Mössbauer spectroscopy and vibrating sample magnetometer. Mössbauer spectra and the hyperfine field distributions of all the samples show the presence of both magnetic and paramagnetic components in the samples. The corresponding bulk magnetization studies also show that the Al rich samples are also ferromagnetic, which can be attributed to the presence of disordered Fe-rich phases due to the non-equilibrium process of alloying. In Fe-rich samples, the formation of an off stoichiometric Fe3Al phase is favored while in the case of Al-rich samples both Al-rich phases and clustering of Fe and Al atoms are present. The systematic variation in the magnetic properties has been qualitatively correlated with the evolution of microstructure, reduction in grain size (obtained using transmission electron microscopy) and enhanced intergranular exchange coupling.

scholarly journals Effect of Co Substitution on Crystallization and Magnetic Behavior of Fe85.45−xCoxCu0.55B14 Metallic Glass

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 919
Author(s):  
Lukasz Hawelek ◽  
Tymon Warski ◽  
Patryk Wlodarczyk ◽  
Marcin Polak ◽  
Przemyslaw Zackiewicz ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Behavior ◽  
Magnetic Core ◽  
Scanning Calorimetry ◽  
Cu Content ◽  
Transmission Electron ◽  
Heat Treated ◽  
Core Losses ◽  
Diffraction Patterns ◽  
Nanocrystalline Phases

The effects of Co for Fe substitution on magnetic properties, thermal stability and crystal structure of Fe85.45−xCoxCu0.55B14 (x = 0, 2.5, 5, 7.5, 10) melt spun amorphous alloys were investigated. The Cu content was firstly optimized to minimize the energy of amorphous phase formation by the use of a thermodynamic approach. The formation of crystalline α-Fe type phase has been described using differential scanning calorimetry, X-ray diffractometry and transmission electron microscopy. The classical heat treatment process (with heating rate 10 °C/min) in vacuum for wound toroidal cores was optimized in the temperature range from 280 to 430 °C in order to obtain the best magnetic properties (magnetic saturation Bs and coercivity Hc obtained from the B(H) dependencies) at 50 Hz frequency. For optimal heat-treated samples, the complex magnetic permeability in the frequencies 104–108 Hz at room temperature was measured. Finally, magnetic core losses were obtained for 1 T/50 Hz and 1.5 T/50 Hz values for samples annealed at T = 310 °C. An analysis of transmission electron microscope images and electron diffraction patterns confirmed that high magnetic parameters are related to the coexistence of the amorphous and nanocrystalline phases.

scholarly journals Quantitative analysis of magnetic spin and orbital moments from an oxidized iron (1 1 0) surface using electron magnetic circular dichroism

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Thomas Thersleff ◽  
Jan Rusz ◽  
Stefano Rubino ◽  
Björgvin Hjörvarsson ◽  
Yasuo Ito ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Circular Dichroism ◽  
Magnetic Circular Dichroism ◽  
Strong Dependence ◽  
Magnetic Behavior ◽  
Spin Moment ◽  
Transmission Electron ◽  
Oxidized Iron ◽  
Magnetic Spin ◽  
Circular Dichroïsm

Abstract Understanding the ramifications of reduced crystalline symmetry on magnetic behavior is a critical step in improving our understanding of nanoscale and interfacial magnetism. However, investigations of such effects are often controversial largely due to the challenges inherent in directly correlating nanoscale stoichiometry and structure to magnetic behavior. Here, we describe how to use Transmission Electron Microscope (TEM) to obtain Electron Magnetic Circular Dichroism (EMCD) signals as a function of scattering angle to locally probe the magnetic behavior of thin oxide layers grown on an Fe (1 1 0) surface. Experiments and simulations both reveal a strong dependence of the magnetic orbital to spin ratio on its scattering vector in reciprocal space. We exploit this variation to extract the magnetic properties of the oxide cladding layer, showing that it locally may exhibit an enhanced orbital to spin moment ratio. This finding is supported here by both spatially and angularly resolved EMCD measurements, opening up the way for compelling investigations into how magnetic properties are affected by nanoscale features.

scholarly journals Entropic formation of a thermodynamically stable colloidal quasicrystal with negligible phason strain

2021 ◽  
Vol 118 (7) ◽  
pp. e2011799118
Author(s):  
Kwanghwi Je ◽  
Sangmin Lee ◽  
Erin G. Teich ◽  
Michael Engel ◽  
Sharon C. Glotzer
Keyword(s):  
Soft Matter ◽  
Colloidal Particles ◽  
Strain Relaxation ◽  
Recognition Algorithm ◽  
Structural Quality ◽  
Pattern Recognition Algorithm ◽  
Transmission Electron ◽  
Energetic Interactions ◽  
High Degree

Quasicrystals have been discovered in a variety of materials ranging from metals to polymers. Yet, why and how they form is incompletely understood. In situ transmission electron microscopy of alloy quasicrystal formation in metals suggests an error-and-repair mechanism, whereby quasiperiodic crystals grow imperfectly with phason strain present, and only perfect themselves later into a high-quality quasicrystal with negligible phason strain. The growth mechanism has not been investigated for other types of quasicrystals, such as dendrimeric, polymeric, or colloidal quasicrystals. Soft-matter quasicrystals typically result from entropic, rather than energetic, interactions, and are not usually grown (either in laboratories or in silico) into large-volume quasicrystals. Consequently, it is unknown whether soft-matter quasicrystals form with the high degree of structural quality found in metal alloy quasicrystals. Here, we investigate the entropically driven growth of colloidal dodecagonal quasicrystals (DQCs) via computer simulation of systems of hard tetrahedra, which are simple models for anisotropic colloidal particles that form a quasicrystal. Using a pattern recognition algorithm applied to particle trajectories during DQC growth, we analyze phason strain to follow the evolution of quasiperiodic order. As in alloys, we observe high structural quality; DQCs with low phason strain crystallize directly from the melt and only require minimal further reduction of phason strain. We also observe transformation from a denser approximant to the DQC via continuous phason strain relaxation. Our results demonstrate that soft-matter quasicrystals dominated by entropy can be thermodynamically stable and grown with high structural quality––just like their alloy quasicrystal counterparts.

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