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Vandenberghe, R. E.; Barrero, C. A.; Costa, Geraldo Magela da; San, E. Van; Grave, E. De

doi:10.1023/a:1012603603203

Cited by 197 publications

(77 citation statements)

References 39 publications

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“…It is remarkable that the quadrupole shift is very similar to that observed at room temperature, indicating that the Morin transition has been totally suppressed in the present case. As reported previously, [19,20] the presence of structural defects, hydroxyl groups, or isomorphous substitutions can account for the absence of the Morin transition. The second weakest sextet is associated with the presence of maghemite, which appears to be totally blocked at this temperature.…”

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confidence: 61%

A Facile Synthetic Route for the Preparation of Superparamagnetic Iron Oxide Nanorods and Nanorices with Tunable Surface Functionality

et al. 2008

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A simple procedure is used to prepare anisometric iron oxide nanoparticlesexhibiting superparamagnetic behavior. The figure shows the nanorod/nanorice morphology of these novel structures. Superparamagnetism is engineered in these structures by favoring thermally activated processes by adopting small particle sizes, introducing defects, and doping with cations. Positively and negatively charged particles are obtained by varying the surface coating.

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confidence: 61%

A Facile Synthetic Route for the Preparation of Superparamagnetic Iron Oxide Nanorods and Nanorices with Tunable Surface Functionality

et al. 2008

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“…1 X-ray absorption near edge spectra (XANES). Inset shows peak positions in more detail of compounds and phases (Vandenberghe et al 2000;Zboril et al 2002). The Mössbauer spectra of the GA and FT samples obtained are shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

et al. 2013

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A study of the magnetic behavior of maghemite nanoparticles (NPs) in polyvinyl alcohol (PVA) polymer matrices prepared by physical crosslinking is reported. The magnetic nanocomposites (ferrogels) were obtained by the in situ co-precipitation of iron salts in the presence of PVA polymer, and subsequently subjected to freezing-thawing cycles. The magnetic behavior of these ferrogels was compared with that of similar systems synthesized using the glutaraldehyde. This type of chemical crosslinking agents presents several disadvantages due to the presence of residual toxic molecules in the gel, which are undesirable for biological applications. Characteristic particle size determined by several techniques are in the range 7.9-9.3 nm. The iron oxidation state in the NPs was studied by X-ray absorption spectroscopy. Mössbauer measurements showed that the NP magnetic moments present collective magnetic excitations and superparamagnetic relaxations. The blocking and irreversibility temperatures of the NPs in the ferrogels, and the magnetic anisotropy constant, were obtained from magnetic measurements. An empirical model including two magnetic contributions (large NPs slightly departed from thermodynamic equilibrium below 200 K, and small NPs at thermodynamic equilibrium) was used to fit the experimental magnetization curves. A deviation from the superparamagnetic regime was observed. This deviation was explained on the basis of an interacting superparamagnetic model. From this model, relevant magnetic and structural properties were obtained, such as the magnitude order of the dipolar interaction energy, the NPs magnetic moment, and the number of NPs per ferrogel mass unit. This study contributes to the understanding of the basic physics of a new class of materials that could emerge from the PVA-based magnetic ferrogels.

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“…In an ICEMS RT spectrum of stoichiometric magnetite, two sextet components are detected corresponding to iron in the octahedral and tetrahedral positions, respectively. 39 In such spectrum, the component corresponding to octahedral iron presents parameters …”

Section: 4mentioning

confidence: 99%

Room temperature in-plane ⟨100⟩ magnetic easy axis for Fe3O4/SrTiO3(001):Nb grown by infrared pulsed laser deposition

Monti¹,

Sanz²,

Oujja³

et al. 2013

Journal of Applied Physics

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We examine the magnetic easy-axis directions of stoichiometric magnetite films grown on SrTiO 3 :Nb by infrared pulsed-laser deposition. Spin-polarized low-energy electron microscopy reveals that the individual magnetic domains are magnetized along the in-plane h100i film directions. Magneto-optical Kerr effect measurements show that the maxima of the remanence and coercivity are also along in-plane h100i film directions. This easy-axis orientation differs from bulk magnetite and films prepared by other techniques, establishing that the magnetic anisotropy can be tuned by film growth. 2 It is a highly correlated electron material that presents a prototypical metal-insulator transition close to 120 K (the Verwey transition 3,4 ). At low temperature it becomes ferroelectric, and thus, multiferroic. 5,6 A bad metal at room temperature (RT), but predicted to be a half-metal with only the minority-spin band crossing the Fermi level, 7 it has been considered a promising material for spintronic applications as an spin-injector 8,9 or as part of a spin-valve.10,11 For such purposes, it is often desired to obtain highly perfect magnetite films on different oxide substrates. In particular, SrTiO 3 is a very attractive material in the microelectronics industry and can be doped to provide either an insulating or metallic substrate. In consequence, there is interest in the magnetic and transport properties of magnetite films grown on SrTiO 3 , both Nb-doped 12-16 and undoped, 17-23 by using techniques such as molecular beam epitaxy or pulsed-laser deposition (PLD).The magnetization bulk easy-axis directions of Fe 3 O 4 at RT are the cubic h111i ones. The first order anisotropy constant changes sign upon cooling to 130 K, temperature below which the easy axis are the h100i directions, [24][25][26] down to Verwey transition at $120 K where the structure changes from cubic to monoclinic. Thus, in the (001) surface of bulk samples, the magnetization is expected to lie along the projection of the bulk h111i on the (001) surface, i.e., the in-plane h110i directions, 27 an expectation confirmed by spin-polarized low-energy electron microscopy observations (SPLEEM). 28 Most magnetic studies of thin films on SrTiO 3 are performed by techniques such as magneto-optical Kerr effect (MOKE), and SQUID or vibrating-sample magnetometry (VSM), all of which average over the full thickness of the magnetite film. 16,17,19,20,23 In most cases, h110i in-plane directions are reported for the easy-axis, 17,29,30 although some works indicate in-plane isotropic films. 20 There are several reports of real-space imaging of the surface domains by magnetic-force microscopy (MFM), 16,19,23 showing domains of about 60-100 nm in size, similar to the observed grain size, but they do not identify the local domain magnetization direction. On other (100) substrates, h110i easy-axis directions are also usually reported. 31,32 Although attempts have been made to modify the easy axis orientation by the use of piezoelectric substrates 29 or through growth on ste...

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Cited by 197 publications

References 39 publications

A Facile Synthetic Route for the Preparation of Superparamagnetic Iron Oxide Nanorods and Nanorices with Tunable Surface Functionality

A Facile Synthetic Route for the Preparation of Superparamagnetic Iron Oxide Nanorods and Nanorices with Tunable Surface Functionality

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

Room temperature in-plane ⟨100⟩ magnetic easy axis for Fe3O4/SrTiO3(001):Nb grown by infrared pulsed laser deposition

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