Embedded iron nano-clusters prepared by Fe ion implantation into MgO crystals

Hayashi, Naoaki; Sakamoto, Isao; Toriyama, T.; Wakabayashi, Hidetsugu; Okada, Tatsuya; Kuriyama, K.

doi:10.1016/s0257-8972(03)00198-1

Cited by 17 publications

(8 citation statements)

References 8 publications

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“…47 Studies of Fe implantation in MgO typically require energies in the range of 50-100 keV or higher. 48 Another interesting possibility is the existence of d 0 ferromagnetism in MgO as suggested recently in both nanoparticles 49,50 and thin films. 51 We have not found any evidence of Mg vacancies in our single crystalline substrates and, therefore, this effect may be ruled out.…”

Section: Resultsmentioning

confidence: 91%

Origin of the giant magnetic moment in epitaxialFe3O4thin films

et al. 2010

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We study the enhanced magnetic moment observed in epitaxial magnetite ͑Fe 3 O 4 ͒ ultrathin films ͑t Ͻ 15 nm͒ grown on MgO ͑001͒ substrates by means of pulsed laser deposition. The Fe 3 O 4 ͑001͒ thin films exhibit high crystallinity, low roughness, and sharp interfaces with the substrate, and the existence of the Verwey transition at thicknesses down to 4 nm. The evolution of the Verwey transition temperature with film thickness shows a dependence with the antiphase boundaries density. Superconducting quantum interference device ͑SQUID͒ and vibrating sample magnetometry measurements in ultrathin films show a magnetic moment much higher than the bulk magnetite value. In order to study the origin of this anomalous magnetic moment, polarized neutron reflectivity ͑PNR͒, and x-ray magnetic circular dichroism ͑XMCD͒ experiments have been performed, indicating a decrease in the magnetization with decreasing sample thickness. X-ray photoemission spectroscopy measurements show no metallic Fe clusters present in the magnetite thin films. Through inductively coupled plasma mass spectroscopy and SQUID magnetometry measurements performed in commercial MgO ͑001͒ substrates, the presence of Fe impurities embedded within the substrates has been observed. Once the substrate contribution has been corrected, a decrease in the magnetic moment of magnetite thin films with decreasing thickness is found, in good agreement with the PNR and XMCD measurements. Our experiments suggest that the origin of the enhanced magnetic moment is not intrinsic to magnetite but due to the presence of Fe impurities in the MgO substrates.

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Section: Resultsmentioning

confidence: 91%

Origin of the giant magnetic moment in epitaxialFe3O4thin films

et al. 2010

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“…The isomer shift of Fe located at Mg 2 Ni grain boundary increases very slightly with the hydrogenation (Mg 2 Ni→Mg 2 NiH 4 ) (Table I), while the quadrupole splitting remains practically unchanged, suggesting the same strength of local distortion of Fe environment at the Mg 2 Ni or Mg 2 NiH 4 grain boundaries. Taking into account the isomer shift and quadrupole splitting values of Table I, the Fe 3+ doublet can be assigned to Fe dissolved into Mg or to some Fe complex with cationic vacancies in MgO matrix [16] or still to some Fe 3+ oxide in superparamagnetic relaxation state. The last two assignments are more probable, because in hydrogenated samples Fe tends to segregate from Mg-Ni matrix and to form metallic iron.…”

Section: Resultsmentioning

confidence: 99%

Mössbauer study of Mg–Ni(Fe) alloys processed as materials for solid state hydrogen storage

et al. 2006

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Mg-Ni-Fe magnesium-rich intermetallic compounds were prepared following two distinct routes. A Mg 88 Ni 11 Fe 1 sample (A) was prepared by melt spinning Mg-Ni-Fe pellets and then by high-energy ball milling for 6 h the obtained ribbons. A (MgH 2 ) 88 Ni 11 Fe 1 sample (B) was obtained by high-energy ball milling for 20 h a mixture of Ni, Fe and MgH 2 powders in the due proportions. A SPEX8000 shaker mill with a 10:1 ball to powder ratio was used for milling in argon atmosphere. The samples were submitted to repeated hydrogen absorption/desorption cycles in a Sievert type gas-solid reaction controller at temperatures in the range 520÷590 K and a maximum pressure of 2.5 MPa during absorption. The samples were analysed before and after the hydrogen absorption/ desorption cycles by X-ray diffraction and Mössbauer spectroscopy. The results concerning the hydrogen storage properties of the studied compounds are discussed in connection with the micro-structural characteristics found by means of the used analytical techniques. The improved kinetics of hydrogen desorption for sample A, in comparison to sample B, has been ascribed to the different behaviour of iron atoms in the two cases, as proved by Mössbauer spectroscopy. In fact, iron results homogeneously distributed in sample A, partly at the Mg 2 Ni grain boundaries, with catalytic effect on the gas-solid reaction; in sample B, instead, iron is dispersed inside the hydride powder as metallic iron or superparamagnetic iron.

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“…Ferromagnetic nanoparticles can be potentially used for ultrahigh density data storage devices, 1-3 as well in magnetooptic and magnetotransport systems. 4,5 Industrial application of ferromagnetic nanoparticles in data storage requires, however, their fixed crystallographic orientation with respect to the host matrix. 6 Magnetic nanoparticles embedded into MgO, TiO 2 , ZnO, and other crystals fulfill this condition, being epitaxially related to the surrounding matrix.…”

Section: Introductionmentioning

confidence: 99%

Fe nanoparticles embedded in MgO crystals

Shalimov

Potzger

Geiger

et al. 2009

Journal of Applied Physics

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Iron nanoparticles embedded in MgO crystals were synthesized by Fe+ ion implantation at an energy of 100 keV and varying fluences from 3×1016 to 3×1017 cm−2. Investigations of structural and magnetic properties of Fe nanoparticles have been performed using magnetometry, x-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy, as well as by theoretical Preisach modeling of bistable magnetic systems. It has been found that α- and γ-Fe nanoparticles are formed for all fluences. The content of the α-Fe phase increases at higher fluences and after annealing. The influence of postimplantation annealing at 800 °C in vacuum and under enhanced hydrostatic pressure on the formation of nanoparticles has been analyzed.

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Embedded iron nano-clusters prepared by Fe ion implantation into MgO crystals

Cited by 17 publications

References 8 publications

Origin of the giant magnetic moment in epitaxialFe3O4thin films

Origin of the giant magnetic moment in epitaxialFe3O4thin films

Mössbauer study of Mg–Ni(Fe) alloys processed as materials for solid state hydrogen storage

Fe nanoparticles embedded in MgO crystals

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