Properties and applications of magnetic nanoparticles
The rapidly growing area of information technology constantly demands higher storage densities. Creating ever smaller magnetic structures is an important issue and the magic Terabits per square inch density an ambitious goal. This has led to a dramatically enhanced interest in magnetic nanoparticles and their behavior with a view to being able to design and control their properties to make them suitable for information storage. The toolbox for preparing such particles includes both physical and chemical related approaches with top down and bottom up preparation methods. Preparation, however, has to be accompanied by strict quality control including the arrangements of particles, their shape, structure and magnetic properties. The close interrelation between preparation, properties and control of these particles is emphasized in this Thematic Series. Other applications include the much broader field of sensor technology, especially for medical diagnostics.
- Full Research Paper
- Published 22 Nov 2010
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Scheme 1: Preparation of NPs by a reverse micelle technique. PS-b-P2VP or PS-b-P4VP is dispersed in anhydrous...
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Figure 1: CoCl2 loaded PS(1779)-b-P2VP(857) reverse micelles deposited at different dip-coating velocities; (...
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Figure 2: Co NPs prepared from CoCl2-loaded PS(1779)-b-P2VP(857) reverse micelles deposited on a Si AFM-tip b...
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Figure 3: Fe (left column) and Co (right column) NPs prepared from PS(312)-P2VP(71) (upper panels) and PS(177...
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Figure 4: SEM micrographs of FePt NPs with 2.6 nm, 4.5 nm, and 9.4 nm diameter (top panels) and their AFM hei...
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Figure 5: Photoelectron spectroscopy of Co-precursor loaded PS(1779)-P2VP(857) reverse micelles after differe...
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Figure 6: Pt-4f and Fe-2p XPS spectra of 9.8 nm FePt particles before and after exposure to ambient air for 2...
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Figure 7: TEM images of 3 nm FePt NPs on Si/SiO2 after annealing at 650 °C for 90 min. (a) Bright-field TEM i...
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Figure 8: Aberration corrected HRTEM images of FePt particles seen along [100] direction. The L10 ordering al...
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Figure 9: Aberration corrected HR-TEM images of about 8 nm FePt NPs in [101] orientation. Crystal defects such as ...
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Figure 10: (a) Schematics of the compensation approach: Temperature dependence of the magnetic susceptibility ...
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Figure 11: (a) DC-demagnetization and isothermal remanent magnetization of 8 nm Co particles measured by SQUID...
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Figure 12: Element-specific magnetic hysteresis loops of 5.8 nm FePt NPs taken at the Fe-L3 edge at T = 11 K a...
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Figure 13: Coercive field at T = 300 K as function of the diameter of FePt NPs after annealing for 30 min at T...
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Figure 14: Experimental hysteresis loops of 5.8 nm FePt NPs at 11 K and simulations using a bimodal Gaussian K...
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Figure 15: Distributions of the effective anisotropy Keff for arrays of differently sized NPs used for simulat...
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Figure 16: (a) Coercive fields at T = 11 K and T = 300 K as function of 30 min annealing time at temperature TA...
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Figure 17: Co-L3,2 XA and XMCD spectra of 5.6 nm Co56Pt44 NPs after annealing at 700 °C taken at external fiel...
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Figure 18: Element-specific magnetic hysteresis loops of 5.8 nm Co56Pt44 NPs taken at the Co-L3 edge maximum d...
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Figure 19: SEM images of 8 nm Co-based NP after oxygen plasma (a) and after Au photoseeding of reduced particl...
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- Published 22 Nov 2010
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Figure 1: Schematic illustration of magnetic fluctuations in a nanoparticle. At low temperatures the directio...
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Figure 2: Schematic illustration of spin waves in macroscopic crystals (red arrows) and uniform excitations i...
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Figure 3: The reduced average magnetic hyperfine field
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as a function of temperature for particles of magneti...
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Figure 4: Parameters derived from inelastic neutron scattering data for 4.0 nm particles of maghemite: (a) En...
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Figure 5: The observed median hyperfine field for 20 nm hematite nanoparticles as a function of temperature. ...
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Figure 6: Inelastic neutron scattering data for 15 nm hematite particles measured at the scattering vector Q ...
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Figure 7: Schematic illustration of the uniform mode in antiferromagnetic nanoparticles: (a) At low temperatu...
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- Full Research Paper
- Published 22 Nov 2010
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Figure 1: Schematic representation of the experimental setup: the sample is placed behind the back focal plan...
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Figure 2: Evolution of the CoPt NPs size and shape as a function of the number of laser pulses. TEM images an...
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Figure 3: Evolution of the CoPt NPs size, shape, and crystalline structure during flash laser annealing. TEM ...
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- Published 22 Nov 2010
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Figure 1: Schematic representation of the precursor concentration according to the LaMer model. The blue line...
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Figure 2: Interaction of different ligands with the surface of a metallic nanoparticle. There is only a singl...
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Figure 3: Transmission electron microscopy (TEM) images of Co particles of various sizes and morphologies syn...
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Figure 4: (a) Nanoparticles synthesized by micro emulsion approach and (b) by employment of the synthetic pro...
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Figure 5: Hypothesized particle formation during the biomineralization process in magnetotactic bacteria (in ...
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Figure 6: Dynamic evolution of different concentrations for the decay rates k1 = 0.00753 s−1 and k2 = 0.0136 s...
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Figure 7: Co particles with a diameter of 4.9 and 10 nm measured at room temperature shortly after the prepar...
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Figure 8: Self-assembled FeCo nanoparticles with different dimensions: (a) The 2D-monolayer of 4.6 nm sized s...
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Figure 9: (a) Scheme of two particles with a metallic core of radius R surrounded by a ligand shell of the th...
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Figure 10: Images of self-assembled spherical Co nanoparticles: (a) TEM image of a bimodal distribution; large...
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Figure 11: TEM images of self-assembled Co particles with different morphologies. Nanodisks exhibit a typical ...
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Figure 12: Schematic representation of the tunnel magnetoresistance (TMR) sensor setup for the detection of mu...
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Figure 13: Properties of the magnetoresistive sensors. (a) Comparison between experimental and numerical data....
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Figure 14: GMR response of a monolayer consisting of 8 nm Co particles covered by a thin Cu film. Measurements...
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Figure 15: Magnetoresistance measurements at room temperature on a granular system consisting of Co nanopartic...
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Figure 16: Magnetization evolution of four interacting magnetic dipoles arranged in the corners of a square wi...
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Figure 17: Equilibrium states of 10 × 10-particle arrays with cubic and hexagonal symmetry. Magnetic moments i...
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Figure 18: Direction dependent responses of different small particle assemblies to an external magnetic field....
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Figure 19: Response maps of a 10 × 10-hexagonal gGMR sensor for a probe particle with Rp = 50 nm and Mp = 500 ...
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Figure 20: Comparison between free (dotted) and hysteretic (line) sensor behavior for cubic and hexagonal symm...
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- Full Research Paper
- Published 01 Dec 2010
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Figure 1: AFM (a) and SEM (b) images showing the self-assembly of the NPs in a close-packed hexagonal structu...
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Figure 2: Top panel: High-resolution TEM cross-section images of non-ion-milled (a) and ion-milled (b) compos...
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Figure 3: Magnetic hysteresis loops at 330 K and 15 K for a monolayer film of nanoparticles (a) and the compo...
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Figure 4: (a) Dark-field TEM image of the cross section NPs/thin-film system showing the CoO layer at the int...
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Figure 5: ZFC/FC magnetic moment vs temperature measured in 500 Oe for a NP monolayer (green squares), non-io...
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Figure 6: Top panel: AFM images of the Co surface for the non-ion-milled (a) and ion-milled (b) composite sys...
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- Published 03 Dec 2010
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Figure 1: WAXS diagram (top) and the related RDF (bottom). Black: experimental spectra of Fe NPs taken at roo...
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Figure 2: WAXS diagram (top) and the related RDF (bottom). Black: Fe NPs taken at room temperature; dark grey...
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Figure 3: XANES spectra taken at room temperature for metallic Fe NPs, compared to a Fe foil reference, and i...
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Figure 4: Top: Mössbauer spectra taken at different temperatures. Bottom: experimental spectra (symbols) take...
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Figure 5: Distributions of the IS and the µ0Hhyp used to fit the experimental Mössbauer spectrum measured at ...
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Figure 6: ZFC-FC magnetizations measured under µoH = 1 mT. Inset shows the extracted temperature dependence o...
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Figure 7: AC susceptibility measured for various frequencies (symbols) and their fits (solid lines).
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Figure 8: Hysteresis loop measured at 2 K. Inset: enlargement near zero field showing the coercive field.
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Figure 9: Magnetization curves in the superparamagnetic regime plotted versus the applied magnetic field (top...
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Figure 10: Relaxation time versus the inverse of temperature.
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Figure 11: FMR spectra collected for various T. Inset displays the evolution of geff versus 1/T.
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- Published 16 Dec 2010
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Figure 1: DMR assay configurations with magnetic nanoparticles (MNPs). (a) Magnetic relaxation switching (MRS...
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Figure 2: Higher r2-relaxivity MNPs developed to improve detection sensitivity of in vitro diagnostics. (a) T...
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Figure 3: Bioorthogonal nanoparticle detection (BOND) strategy for DMR detection. The schematics show the con...
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Figure 4: Miniaturized devices developed for DMR biosensing. (a) The first-generation miniaturized device to ...
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Figure 5: DMR detection of proteins and enzyme activities with MRSw sensors.
(a) Detection of avidin. Biotinyl... -
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Figure 6: DMR detection of bacteria by tagging the bacterial samples with MNPs. (a) Scanning electron microgr...
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Figure 7: Tumor cell detection and profiling with the µNMR device. (a) Human breast cancer cells (BT474) were...
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- Published 28 Dec 2010
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Figure 1: The relaxation time of 4.7 nm Fe100−xCx nearly monodisperse particles suspended in decalin as a fun...
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Figure 2: Schematic illustration of interacting magnetic nanoparticles. (a) Isolated nanoparticles dominated ...
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Figure 3: Mössbauer spectra of 8 nm hematite particles (a) coated (non-interacting) and (b) uncoated (strongl...
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Figure 4: Neutron diffraction data for interacting 8 nm α-Fe2O3 particles obtained at 20 K. The inset shows a...
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Figure 5: The normalized magnetic energy, E(θ)/KV (Equation 9) for different values of the ratio between the interactio...
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Figure 6: Temperature dependence of the median value of the order parameter, b50(T) for interacting 20 nm hem...
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Figure 7: Mössbauer spectra of 8 nm hematite nanoparticles ground in a mortar with η-Al2O3 nanoparticles for ...
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Figure 8: (a) The quadrupole shift of coated (open circles) and uncoated (solid circles) 8 nm hematite partic...
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- Full Research Paper
- Published 17 Jan 2011
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Figure 1: Comparison of simulated ordering kinetics in bulk FePt alloys with results from annealing experimen...
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Figure 2: Evolution of ordering fraction in a free FePt nanoparticle of D = 5 nm compared to the case of bulk...
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Figure 3: Structure of a free 5 nm particle after 30 s of annealing time at 1000 K. Top: Pt atoms are display...
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Figure 4: Snapshots of supported FePt nanoparticles illustrating the different interface energetics investiga...
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Figure 5: Bottom panel: Evolution of LRO parameter with annealing time at 1000 K in free and supported FePt n...
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Figure 6: Evolution of LRO parameter with annealing time at 1000 K in free and supported FePt nanoparticles w...
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- Published 21 Jan 2011
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Figure 1: (a) Schematic drawing of the ACIS. (b) TEM image of a typical nanoparticle deposit on a carbon coat...
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Figure 2: (a) X-ray absorption spectra of the Ni(111) substrate. Inset: Schematics of the experiment. (b) XAS...
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Figure 3: (a) Schematics of the in situ RHEED setup [58] (b) and (c): RHEED diffraction patterns from (b) larger ...
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Figure 4: (a) STM image of mass-filtered Fe nanoparticles (mean diameter of 7 nm) deposited onto W(110). Tunn...
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- Published 16 Mar 2011
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Figure 1: Energies of Mn–Pt clusters of various morphologies and sizes. The energy reference is marked by the...
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Figure 2: Energetic order (left panel) and magnetization (right panel, left scale) of ternary 561 atom Fe–Mn–...
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Figure 3: Lattice constant (left panel) and c/a ratio (right panel) of ternary 561-atom Fe–Mn–Pt clusters wit...
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- Published 11 May 2011
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Figure 1: Effective backscattering amplitude of O, Fe, and Pt as a function of wave number and phase shift. A...
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Figure 2: Experimental EXAFS data measured at the Pt L3 absorption edge of FePt bulk material at room tempera...
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Figure 3: Real part of a Gabor mother wavelet (red curve) and baby wavelets generated by scaling and shifting...
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Figure 4: Two different sample signals (upper panel) that show the same radial distance function after FT (ce...
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Figure 5: WT of room temperature EXAFS data for Fe (upper graphic) and Pt (lower graphic) reference samples m...
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Figure 6: Room temperature EXAFS data of FePt bulk material (left panel) and nanoparticles (right panel) meas...
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Figure 7: WT of room temperature EXAFS data of FePt nanoparticles measured at the Pt L3 (upper graphic) and F...
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Figure 8: Composition dependence of spin and orbital magnetic moments at the Fe and Pt sites in chemically di...
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Figure 9: Dependence of spin and orbital magnetic moments at the Fe and Pt sites in chemically disordered FeP...
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- Published 01 Jun 2011
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Figure 1: Scanning electron micrograph of Fe nanoparticles deposited on Si. The average particle size observe...
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Figure 2: Transmission electron microscope image of Fe nanoparticles (dark contrast) coated with a thin SiOx ...
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Figure 3: Electron diffraction pattern of the Fe nanoparticles. The Miller indices of the respective lattice ...
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Figure 4: X-ray diffraction patterns (Cu Kα radiation) of Fe nanoparticles embedded in a Cu film on a Ta subs...
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Figure 5: In-plane hysteresis curves of the embedded Fe nanoparticles measured at 10 K in as-prepared state (...
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Figure 6: In-plane hysteresis curves of the embedded Fe nanoparticles after loading of the Ta substrate with ...
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Figure 7: ZFC (circles) and FC (squares) magnetization curves of the Fe nanoparticles embedded in Cu film in ...
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