Effect of heat treatment on magnetic properties and morphology of iron particles

Sueyoshi, T.; Tashita, K.; Hirai, S.; Kishimoto, Mikio; Hayashi, Yamato; Amemiya, M.

doi:10.1063/1.330910

Cited by 15 publications

(8 citation statements)

References 5 publications

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“…Thus, the Al/Fe + Co + Al mole ratio increased from 8% for the G CoAl sample to 33% for sample Fe CoAl (figure 5), indicating a further and more important enrichment of Al cations in the particle outer layers during its reduction process, which explains its role in avoiding interparticle sintering. In addition, it was observed that the proportion of cobalt in the particle outer layers decreased from goethite to iron for both Fe Co and Fe CoAl samples, respectively (figure 5), which suggested the diffusion of this cation to the inner part of the iron particles and, thereby, the formation of Fe-Co alloy, as previously observed by other authors [14,15]. Finally, the position observed for the Fe 2p 3/2 (710.3 eV) and Co 2p 3/2 (780.3 eV) XPS peaks (data not shown) was consistent with the presence of oxidized iron and cobalt in the particle outer layers, which could consist of a ferrimagnetic spinel phase similar to that suggested for Al-doped iron from Mössbauer studies [18].…”

Section: Preparation Of Iron Metal Particlessupporting

confidence: 79%

“…Several studies have been carried out on the synthesis of Fe-Co MP from Co(II) adsorbed onto acicular goethite precursors [12,14,15]. However, this process involves the use of high temperatures (∼700 • C) to diffuse the Co toward the inner part of iron particles, leading to sintering between particles and the particles losing their acicular shape.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of acicular Fe–Co nanoparticles and the effect of Al addition on their magnetic properties

et al. 2004

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We have obtained Al(III)-protected Fe-Co metal nanoparticles with acicular shape by thermal reduction with hydrogen from Al(III)-Co(II)-codoped acicular goethite precursors prepared by oxidation with air of a FeSO 4 solution containing Al(NO 3) 3 and Co(NO 3) 3 precipitated with Na 2 CO 3. These precursor particles were smaller (∼110 nm in length) than those prepared by a previously reported procedure, resulting in smaller metal particles (∼70 nm in length) suitable for high-density magnetic recording media in which higher bit-packing densities could be obtained. The location of Co and Al in the goethite precursors, as well as in the final metal particles, have been studied for a better understanding of role that these elements play in the microstructural features and the magnetic properties of the final metal particles. It was found that the Al content in the particle outer layers was enhanced during the reduction process, while cobalt diffuses toward the inner part of iron nanoparticles forming an Fe-Co alloy. The incorporation of cobalt helps to increase the magnetization saturation because it avoids corrosion and minimizes the growth of the iron crystals. The presence of Al(III) in the particle outer layers of the precursors inhibited the growth of iron crystals and preserved the acicular shape during the reduction process, which has a very favourable effect on the coercivity and the squareness of the metal samples.

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Section: Preparation Of Iron Metal Particlessupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Synthesis of acicular Fe–Co nanoparticles and the effect of Al addition on their magnetic properties

et al. 2004

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“…Giessen et al 1) reported that magnetic properties can be improved since in the case of absorbing Co 2þ and Ag þ on the oxide surface, the reduction rate at a low temperature becomes large, and in the case of absorbing Sn 2þ on the oxide particle, the reduction rate drops. Sueyoshi et al [2][3][4][5] reported that the iron particles prepared by reduction of silica-coated hematite particles showed excellent acicular shape and magnetic properties because of a diminished sintering of the iron particles. Ishikawa et al 6) also reported that the similar experimental results were obtained in the reduction of silica and cobalt coated hematite particles.…”

Section: Introductionmentioning

confidence: 99%

Production Conditions of Acicular Magnetic Metal Nanoparticles for Magnetic Recording

2005

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Hydrogen reduction conditions of -Fe 2 O 3 particles and surface passivation conditions of metal nanoparticles obtained through a hydrogen reduction process of acicular -Fe 2 O 3 particles and a slow oxidation process in a low oxygen concentration have been studied in order to determine optimum production conditions of acicular magnetic metal nanoparticles utilized for magnetic recording.Acicular magnetic metal nanoparticles were produced by using the surface-treated acicular -FeOOH nanoparticles containing 12.6 at%Co-9.4 at%Si-7.0 at%Al under the condition of 823 K in temperature of dehydration of -FeOOH particles by heating, 5 Â 10 À6 m 3 (STP)Ás À1 in flow rate, 50 mol%H 2 -50 mol%Ar in composition of a reducing gas, and 823 K in reduction temperature. The resulting reduced metal particles are composed of either a single crystal or polycrystals. The inside of the particles was a reduced dense metal phase in which the crystal growth with neither defect nor pore was sufficiently proceeded.The surface oxide layer of metal particles which is formed by the slow oxidation results in a spinel structure of Fe 3 O 4 . The metallic core was entirely coated by the surface oxide layer, and it was observed that the dense crystal having no defect; pore and so forth inside the oxide layer was sufficiently grown. It is assumed that a passivation layer possessing a higher corrosion-resistant property can be obtained with a thicker surface oxide layer, since the oxide layer on the surface of the metal nanoparticle becomes thicker with higher temperature of slow oxidation.Acicular magnetic metal nanoparticles having the excellent property of corrosion resistance were able to be produced under the condition of 338 K in oxidation temperature, 5 Â 10 À6 m 3 (STP)Ás À1 in flow rate and 0.5 mol%O 2 -99.5 mol%N 2 in composition of oxidizing gas.

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“…The acicular geothi te was dehydrated ln air, and reduced in hydrogen gas to iron acicular particles (7) • The reduction temperature was 450°C for sample A and 500°C for sample B. Figure 3 shows an example of TEM micrograph of sample A.…”

Section: Resultsmentioning

confidence: 99%

Determination of the Anisotropy Field Distribution of Magnetic Powder Using VSM

Kitahata

Kishimoto

1991

J. Magn. Soc. Jpn.

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Effect of heat treatment on magnetic properties and morphology of iron particles

Cited by 15 publications

References 5 publications

Synthesis of acicular Fe–Co nanoparticles and the effect of Al addition on their magnetic properties

Synthesis of acicular Fe–Co nanoparticles and the effect of Al addition on their magnetic properties

Production Conditions of Acicular Magnetic Metal Nanoparticles for Magnetic Recording

Determination of the Anisotropy Field Distribution of Magnetic Powder Using VSM

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