Granular Fe–Al2O3 films prepared by self-propagating high temperature synthesis

Мягков, В.Г.; Polyakova, K. P.; Бондаренко, Г. Н.; Polyakov, V. V.

doi:10.1016/s0304-8853(02)01081-8

Cited by 12 publications

(5 citation statements)

References 13 publications

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“…Note the close match between the Faraday effect spectrum observed for samples subjected to heat treatment and the Faraday effect spectrum of a polycrystalline film of magnetite Fe 3 O 4 (Fig. 1, curve 5), obtained by self-propagating high-temperature synthesis [17]. In contrast to the Faraday effect spectra of ferrites containing only 3d 5 ion and characterized by a monotonic decrease in the effect as the wavelength of the light increases, in the case of magnetite we observe a broad, intense maximum in the 700-800 nm region.…”

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confidence: 59%

Effect of heat treatment and concentration of Mn and Fe on the structure of borate glass

et al. 2006

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We have studied the magneto-optic Faraday effect (FE) and electron paramagnetic resonance (EPR) in an aluminum potassium borate glass containing Fe oxides as an impurity in a concentration of 1.5 mass % and Mn impurity in variable concentration from 0 to 1.2 mass %. When manganese oxide is added to the glass composition, the paramagnetic contribution to the Faraday effect increases more slowly than the change in the total concentration of paramagnetic ions, which allows us to hypothesize the appearance of clusters in which the paramagnetic ions are coupled by antiferromagnetic interactions. Formation of clusters upon addition of manganese oxide is confirmed by the change in the nature of the EPR spectra, where we observe a manganese concentration dependence of the distribution of iron atoms with respect to the different positions in the glass matrix. Heat treatment leads to a strong increase in the Faraday effect and a change in the spectral dependences of the Faraday effect and the EPR, which is explained by enlargement of the clusters and appearance of nanoparticles.Introduction. The steady demand for technology in efficient media for controlling a light beam has stimulated the search for and investigation of new material having high magneto-optical quality, in particular in the IR region of the spectrum at wavelengths of 1.0-1.5 µm. Glass containing magnetic nanoparticles can be considered as such a material (see, for example, [1,2]). Creation of glasses with the required microstructure and specified physical properties requires detailed study of the processes of particle formation in all stages of glass manufacture. Usually nanoparticles having a crystalline structure are formed during additional heat treatments of the glass. However, inhomogeneities in the distribution of magnetic ions and the appearance of clusters which are nuclei for the magnetic phase occur even in the initial stages of glass manufacture, and to a significant extent determine the nature of the particles appearing as a result of additional heat treatments. In this work, we have studied a glass with the base composition 22.5K 2 O+ 22.5Al 2 O 3 +55B 2 O 3 , containing Fe 2 O 3 and MnO as impurities. In glasses of this group, magnetic nanoparticles are formed as a result of heat treatments even for low concentrations of paramagnetic additives (≈2.0 mass %) [1, 2]. Therefore, while remaining transparent in the spectral region 800-2500 nm, the glasses are characterized by a significant Faraday effect and a nonlinear field dependence for the Faraday effect. The need to optimize the indicated parameters explains why steady attention has been focused on the processes of nucleation and formation of magnetic inhomogeneities in glasses of this system. EPR is the method most often used for investigation of clusters of S transition metal ions in glasses, for example Fe 3+ (3d 5 , 6 S 5/2 ) [3-6]. The EPR spectra of Fe 3+ ions in glass matrices provide information about the immediate environment of the paramagnetic ion because different lines are obs...

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confidence: 59%

Effect of heat treatment and concentration of Mn and Fe on the structure of borate glass

et al. 2006

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“…It can be associated with one or either of the following hypotheses: (i) supermagnetism due to the reduction of the combustion products crystal sizes to nanometric range [28,29] (the higher combustion front velocities observed in these samples, their higher exothermicities and thermal conductivities originated the reducing of the products crystal growth, as explained before); (ii) the dissolution of Fe (and probably the intermetallic as well) in a non-magnetic matrix, like Al 2 O 3 [26,28,45] or Al [26,32]. Concerning the hypothesis (ii), nanometric iron particles may be stabilized in the alumina matrix [45] and the coexistence of superparamagnetic and magnetic states of iron is possible in this case, being 10 nm the critical size of iron clusters to exhibit superparamagnetism [9]. The hypothesis above can also be supported by the rather easy way that these two samples were crushed when compared to the others.…”

Section: Resultsmentioning

confidence: 86%

Fe2O3/aluminum thermite reaction intermediate and final products characterization

Durães

Costa

Santos³

et al. 2007

Materials Science and Engineering: A

122

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Radial combustion experiments on Fe 2 O 3 /aluminum thermite thin circular samples were conducted. A stoichiometric (Fe 2 O 3 + 2Al) and four over aluminized mixtures were tested. The combustion products were characterized by X-ray diffraction and Mössbauer spectroscopy and the influence of Fe 2 O 3 /aluminum ratio on their composition was assessed. The main products were identified as alumina (␣-Al 2 O 3 ) and iron (Fe). A significant amount of hercynite (FeAl 2 O 4 ) was detected, decreasing with the aluminum excess in the reactants. Close to the sample/confinement interface, where reaction quenching occurs, a non-stoichiometric alumina (Al 2.667 O 4 ) was observed, being its XRD intensity correlated to the hercynite amount. Fe 3 Al intermetallic phase was found in the products of over aluminized mixtures. A reaction mechanism was proposed comprising: (i) Fe 2 O 3 reduction to Fe 3 O 4 and FeO; (ii) Al oxidation to Al 2 O 3 ; (iii) interaction of the remaining Al with Fe 3 O 4 and FeO with formation of iron-aluminates (hercynite) and iron; (iv) for the over aluminized mixtures, incorporation of Al into the iron-aluminates takes place with the formation of iron and alumina and, in parallel, Al reacts with iron to produce intermetallics.

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“…Composite materials consisting of metallic grains of nanometer size embedded in an insulating host matrix exhibit special optical, electrical and magnetic properties [1] which offer various technical applications. The study of magnetic nanogranular systems, such as 3-d metal grains in insulating matrix attracts attention due to their fundamental interest (superparamagnetic behaviour) as well as their potential application in sensors, magnetic recording, etc.…”

Section: Introductionmentioning

confidence: 99%

Nanogranular Co–Al–O films prepared by laser ablation

Chayka

Kraus

Fendrych

et al. 2004

Physica Status Solidi (b)

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PACS 72.25.-b, 75.47.-m, 75.75.+a, 81.15.Fg Nanogranular Co-Al-O films were prepared by pulsed laser deposition from Co x (Al 2 O 3 ) 1-x targets. Three targets, with different Co volume fractions, were used in order to study the influence of the film composition on magnetic and transport properties. The samples deposited on room temperature substrates exhibit a granular structure consisting of Co grains with the size of few nm embedded in an insulating Al 2 O 3 matrix. The magnetic properties show a gradual transition from a low temperature blocked regime to a high temperature superparamagnetic state. It is confirmed by the disappearance of magnetic hysteresis at high temperatures and the temperature dependence of magnetization. Magnetoresistance (MR) higher then 9% at 20 K can be found in Co 26 Al 23 O 51 film.

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Granular Fe–Al2O3 films prepared by self-propagating high temperature synthesis

Cited by 12 publications

References 13 publications

Effect of heat treatment and concentration of Mn and Fe on the structure of borate glass

Effect of heat treatment and concentration of Mn and Fe on the structure of borate glass

Fe2O3/aluminum thermite reaction intermediate and final products characterization

Nanogranular Co–Al–O films prepared by laser ablation

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