Endotaxial α-Fe Nanoparticles in the High-Fluence Iron-Implanted Single-Crystal MgO (original) (raw)
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Preparation and Properties of Iron and Iron Oxide Nanocrystals in MgO Matrix
Hyperfine Interactions, 2006
We have prepared α-iron and magnetite (Fe 3 O 4) nanoparticles in MgO matrix from a mixture of nanocrystalline Fe 2 O 3 with Mg(H,O) powders calcinated in hydrogen. This procedure yielded spherical magnetic nanoparticles embedded in MgO. Transmission electron microscopy and Mössbauer spectroscopy were used for structure and phase analysis. The measurements of magnetic properties showed increased coercivity of the nanocomposite samples. Keywords nanocrystalline materials • magnetite • α-Fe • nanocomposite • magnetic properties.
Effect of Magnesium doping on Structural and Magnetic Properties of Iron oxide thin films
Preparation of thin films consisted of nano structures have been intensively pursued not only for their fundamental scientific interest but also for many technological applications. Spinel ferrites are very important magnetic materials because of their interesting magnetic properties combined with chemical and thermal stability. Apart from the applications of their magnetic properties in magnetic recording, sensors, and photomagnetics, some spinal ferrites especially magnesium ferrite, are used as a heterogeneous catalysts, adsorption and humidity sensors, oxygen sensors and for their photoelectrical properties.The present studies were undertaken with a view to developing a low-cost, efficient method for the preparation of Mg doped iron oxide thin films. X-ray diffraction patterns demonstrate the formation of magnesium iron oxide. The magnetic measurements are made from M‐H hysteresis loops traced at room temperature using vibrating sample magnetometer (VSM). Ferrites in the nanoregime are found to behave as single domain.
Stability and Local Environment of Iron in Vapor Phase Grown MgO Nanocrystals
The Journal of Physical Chemistry C, 2017
Metallocene injection into a metal combustion flame has been used for trapping transition metal ions inside MgO nanocrystals. Vacuum annealing changes the properties of resulting nonequilibrium solids towards thermodynamic equilibrium and provides means to control impurity localization and, as a result, the nanomaterials' functional properties. By combining structure characterization (X-ray diffraction and Transmission Electron Microscopy) with X-ray absorption spectroscopy and Mössbauer measurements, we tracked valence state and local chemical environment changes of Fe 3+ ions inside vapor phase synthesized MgO nanocrystals. At a concentration of (1.5 ± 0.2) at-% Fe about (1400 ± 200) Fe 3+ ions are effectively diluted within 12 nm sized nanocubes, where they form Fe 3+-Mg 2+ vacancy complexes. Increase of the iron concentration produces additional effects: enhanced ion diffusion and particle coarsening at elevated temperatures, clustering of Fe 3+-Mg 2+ vacancy complexes and, after annealing to T = 1173 K, the nucleation of a magnesioferrite phase that can be detected by X-ray diffraction for 4 at-% samples. At 3 at-% Fe, corresponding impurity ions induce surface energy changes that have a substantial impact on particle shape. With regard to the functional properties associated with transition metal ions in insulating MgO host lattices, the here presented insights underline that annealing-induced reorganization of oxide nanoparticles provides important parameters to control distribution and localization of impurity ions.
Surface Science, 1998
The atomic structure at the Fe 3 O 4 -MgO interface and its role in defining magnetic behaviour in Fe 3 O 4 -MgO multilayers, grown by MBE on MgO(001), has recently been a subject of much interest and controversy: the existence of a ''dead'' magnetic layer at the interface has been proposed to explain why ultra-thin magnetite layers become nonmagnetic. By using Mö ssbauer probe layers it was shown that this model is incorrect. In this paper we present additional structural evidence, from X-ray reflectivity and RHEED measurements, showing that the magnetite layers have the same structure and composition at the interface and in the bulk in agreement with a uniform magnetic structure throughout the entire layer.
Physical Review B, 2009
The interplay between magnetic properties and morphology of thin iron deposits on MgO films grown on Ag͑001͒ was investigated by means of x-ray magnetic circular dichroism and scanning tunneling microscopy ͑STM͒ measurements as a function of the Fe thickness and after postgrowth thermal treatments. The as-grown Fe deposits display a sharp transition as a function of the Fe thickness, corresponding to the development of ferromagnetism at around 4.5 ML. The ferromagnetic phase can be turned into a superparamagnetic phase by means of a thermal treatment. STM measurements allowed us to ascribe the onset of ferromagnetism to the transition from a three-dimensional to a two-dimensional growth mode of the iron deposit and to explain the superparamagnetic behavior in the annealed film as due to the formation of a collection of well-separatedsquared iron particles. Moreover, using the particle shape and size distribution measured by STM, we calculated a value of the magnetic anisotropy of the Fe particles, which is 1 order of magnitude larger than the bulk iron one. This increase is mainly ascribed to the role of surface anisotropy in the Fe nanoparticles and also the role of the dipolar interactions between particles is discussed.
International Journal of Engineering, 2020
Pure and doped magnesium oxide nanoparticles were successfully synthesized employing a sol-gel process. The synthesized nanoparticles were characterized by thermal differential analysis, X-ray powder diffraction, transmission electron microscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometer. X-ray diffraction patterns confirmed the crystallization of MgO structure and correspondingly ratified that the transition metal atoms were incorporated into the MgO host lattice. The crystallite size decreases as the concentration of dopants were augmented. TEM images showed that the particles of pristine magnesium oxide were embedded in the sheet matrix of the graphene-like layer with a size of 22.06 nm. The EDS spectra revealed the presence of carbon in pure MgO nanoparticles, while nickel and chromium were distributed in the host lattice. Based on VSM measurements, room temperature ferromagnetism in pristine MgO-NPs could be ascribed to the presence of either Mg vacancy or carbon atoms. Furthermore, paramagnetic ordering had been observed upon doping. Overall, the prepared MgO-NPs may be found as a potential application in spintronics devices.
Cation Distribution Assisted Tuning of Magnetization in Nanosized Magnesium Ferrite
physica status solidi (a), 2017
The MgFe 2 O 4 nanoparticles are synthesized by combustion method and annealed at different temperatures from 500 to 1000 C. Magnetic properties, morphology, valence states of iron, crystal structure, and microstructure of the samples are investigated systematically by vibrating sample magnetometer, field emission scanning electron microscope, transmission electron microscopy, X-ray absorption spectroscopy, and synchrotron X-ray diffraction. Cation distribution is determined from synchrotron X-ray diffraction data using Rietveld refinement combined with extended X-ray absorption fine structure spectroscopy. The results indicates that all the samples are phasepure with crystallite size ranging from 11 to 41 nm. By adjusting the annealing temperature, cation distribution and particle size can be changed, and consequently leading to the change in structure and magnetic properties. The saturation magnetization of the samples are enhanced significantly compared to that of the bulk material. The variation of magnetic properties is discussed based on cation distribution, particle size, valence state, surface effect, and spin canting.
Applied Physics Letters, 1995
In-plane uniaxial magnetic anisotropy is observed in the magnetic hysteresis loops of ultrathin Fe films grown on MgO͑001͒ by means of oblique-incidence molecular beam epitaxy. The films are deposited from an angle of 45°from the surface normal in the ͑100͒ azimuth toward the ͓100͔. The easy axis of magnetization is perpendicular to the incident Fe-beam direction. A strong structural asymmetry is observed in x-ray photoelectron diffraction and attributed to an oriented morphology that drives the growth-induced magnetic anisotropy. © 1995 American Institute of Physics.