A new inexpensive method for the preparation of acicular precursors for magnetic recording media

Anantharaman, M. R.; Joseph, K V; Keer, H. V.

doi:10.1007/bf02744885

Cited by 4 publications

(4 citation statements)

References 3 publications

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“…g-Fe 2 O 3 particles can be prepared in both acicular (needle like) and spherical form. Needle shaped g-Fe 2 O 3 particles can be synthesized by using complexing media [12] or by starting from Geothite [13]. But in the ultrafine regime, the normal tendency of the particles is to be in spherical shape, so that the contribution from the size anisotropy arising from the needle like shape of the particles is a minimum.…”

Section: Article In Pressmentioning

confidence: 99%

Effect of cobalt doping on the magnetic properties of superparamagnetic γ-Fe2O3-polystyrene nanocomposites

Nair

Mathews

Joy

et al. 2004

Journal of Magnetism and Magnetic Materials

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Superparamagnetic nanocomposites based on g-Fe 2 O 3 and sulphonated polystyrene have been synthesized by ion exchange process and the preparation conditions were optimized. Samples were subjected to cycling to study the effect of cycling on the magnetic properties of these composites. The structural and magnetization studies have been carried out. Magnetization studies show the dependence of magnetization on the number of ion exchange cycles. Doping of cobalt at the range in to the g-Fe 2 O 3 lattice was effected in situ and the doping was varied in the atomic percentage range 1-10. The exact amount of cobalt dopant as well as the iron content was estimated by Atomic Absorption Spectroscopy. The effect of cobalt in modifying the properties of the composites was then studied and the results indicate that the coercivity can be tuned by the amount of cobalt in the composites. The tuning of both the magnetization and the coercivity can be achieved by a combination of cycling of ion exchange and the incorporation of cobalt. r

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Section: Article In Pressmentioning

confidence: 99%

Effect of cobalt doping on the magnetic properties of superparamagnetic γ-Fe2O3-polystyrene nanocomposites

Nair

Mathews

Joy

et al. 2004

Journal of Magnetism and Magnetic Materials

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“…7,8 Of special interest are gamma ferric oxide (␥-Fe 2 O 3 ) particles as they retain important position in magnetic storage media. 9,10 In this article we report on results of annealing sonochemically synthesized ␥-Fe 2 O 3 nanocrystals in different conditions, focusing on two aspects: ͑1͒ changes in the particle size distribution, and the associated variations in magnetic properties of the material during the annealing process and ͑2͒ transformations of ␥-Fe 2 O 3 nanoparticles to other iron-oxide phases caused by annealing at different conditions. Our experiments show that crystallites of ␥-Fe 2 O 3 with different average particle size ranging from 4 to 14 nm can be obtained by controlled annealing in vacuum.…”

Section: Introductionmentioning

confidence: 99%

Annealing study of Fe2O3 nanoparticles: Magnetic size effects and phase transformations

Wolfus

Shaulov

et al. 2002

Journal of Applied Physics

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Sonochemically synthesized Fe 2 O 3 nanoparticles were annealed in air or in vacuum while their magnetization was continuously recorded. Annealing in vacuum at temperatures T a between 240 and 450°C produced nanophases of ␥-Fe 2 O 3 with average particle size ranging from 4 to 14 nm, depending on T a. Phase transformation into ␣-Fe 2 O 3 occurred directly by annealing in air, or via an intermediate Fe 3 O 4 phase by annealing in vacuum at temperatures higher than 450°C. Mapping the correlation between the magnetic properties and the annealing conditions, enables control of the annealing process to obtain nanocrystals of ␥-Fe 2 O 3 , ␣-Fe 2 O 3 , or Fe 3 O 4 with different particle size and magnetic properties.

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“…Most of the particles lie well above the nanometer dimension (Anantharaman et al 1997). However, size, shape and strain dependent optical and magnetic properties are a virgin area where the effect of size and shape can be studied in a single shot if nanosize particles can be synthesized.…”

Section: Introductionmentioning

confidence: 99%

“…But γ-Fe 2 O 3 is a cubic crystal and does not easily form into elongated ellipsoidal particles. Earlier, researchers attempted to synthesize nonspherical precursors using complexing medium (Anantharaman et al 1997). Nucleation will be greatly influenced by external conditions like pH, temperature and constant stirring.…”

Section: Introductionmentioning

confidence: 99%

Strain induced anomalous red shift in mesoscopic iron oxide prepared by a novel technique

et al. 2008

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Nano magnetic oxides are promising candidates for high density magnetic storage and other applications. Nonspherical mesoscopic iron oxide particles are also candidate materials for studying the shape, size and strain induced modifications of various physical properties viz. optical, magnetic and structural. Spherical and nonspherical iron oxides having an aspect ratio, ~2, are synthesized by employing starch and ethylene glycol and starch and water, respectively by a novel technique. Their optical, structural, thermal and magnetic properties are evaluated. A red shift of 0⋅24 eV is observed in the case of nonspherical particles when compared to spherical ones. The red shift is attributed to strain induced changes in internal pressure inside the elongated iron oxide particles. Pressure induced effects are due to the increased overlap of wave functions. Magnetic measurements reveal that particles are superparamagnetic. The marked increase in coercivity in the case of elongated particles is a clear evidence for shape induced anisotropy. The decreased specific saturation magnetization of the samples is explained on the basis of weight percentage of starch, a nonmagnetic component and is verified by TGA and FTIR studies. This technique can be modified for tailoring the aspect ratio and these particles are promising candidates for drug delivery and contrast enhancement agents in magnetic resonance imaging.

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A new inexpensive method for the preparation of acicular precursors for magnetic recording media

Cited by 4 publications

References 3 publications

Effect of cobalt doping on the magnetic properties of superparamagnetic γ-Fe2O3-polystyrene nanocomposites

Effect of cobalt doping on the magnetic properties of superparamagnetic γ-Fe2O3-polystyrene nanocomposites

Annealing study of Fe2O3 nanoparticles: Magnetic size effects and phase transformations

Strain induced anomalous red shift in mesoscopic iron oxide prepared by a novel technique

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