An amorphous magnetically ordered ultra-thin film of Fe2O3 on graphite: Mössbauer spectroscopy

Howard, D.; Nussbaum, Rudi H.

doi:10.1016/0039-6028(80)90041-2

Cited by 13 publications

(13 citation statements)

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“…Such conclusion results particularly from RT Mössbauer spectra showing only a doublet, indicating the absence of magnetic ordering, and from magnetization measurements with no hysteresis of the M(H) curve. The superparamagnetic blocking temperature (T B ) of about 80 K was found by Prozorov et al for amorphous nanopowder prepared by sonochemical method from Fe(CO) 5 . The magnetic behaviour of amorphous Fe 2 O 3 thin films has been interpreted as paramagnetic with the antiferromagnetic ordering below the Neel temperature, which is mentioned to be about 80-100 K [6][7][8][10][11].…”

Section: Introductionmentioning

confidence: 87%

“…Superparamagnetic behaviour at room temperature (RT) has been ascribed to amorphous Fe 2 O 3 nanocomposites and nanopowders varying in the particle size [3][4][5][12][13][14][15]. Such conclusion results particularly from RT Mössbauer spectra showing only a doublet, indicating the absence of magnetic ordering, and from magnetization measurements with no hysteresis of the M(H) curve.…”

Section: Introductionmentioning

confidence: 91%

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Magnetism of amorphous Fe ₂ O ₃ nanopowders synthesized by solid‐state reactions

Zbořil

Machala

Mashlan

et al. 2004

phys. stat. sol. (c)

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PACS 75.50. Kj, 75.75+a, 76.80.+y, 81.07.Wx Monodispersed amorphous Fe 2 O 3 nanoparticles with the size ranging from 1 to 4 nm have been prepared by thermally induced oxidative decomposition of Prussian Blue, Fe 4 [Fe(CN) 6 ] 3 , in air. Amorphous nanopowders exhibit specific magnetic behaviour strongly affected by interparticle interactions and extremely low particle size with a high contribution of the surface anisotropy as illustrated by temperature dependent and external field Mössbauer spectroscopy and magnetization measurements (4-300 K). Some of the properties are in close similarity to those of spin glasses including the fast thermal variation of superparamagnetic fraction in the Mössbauer spectra, or the particle size independence of the blocking temperature, and non-saturation of magnetization even at 5 K and magnetic field of 10 T. The reduced value of internal magnetic hyperfine field (∼49 T at 5 K) and no indications of the tetrahedral Fe 3+ sites in the 5T/5K external field Mössbauer spectra are the principal found differences in comparison with the magnetic behaviour of nanocrystalline γ-Fe 2 O 3 .

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Section: Introductionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 91%

Magnetism of amorphous Fe ₂ O ₃ nanopowders synthesized by solid‐state reactions

Zbořil

Machala

Mashlan

et al. 2004

phys. stat. sol. (c)

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“…137 The RT Mo ¨ssbauer spectrum displays a paramagnetic doublet, with IS Fe ) 0.33-0.35 mm/s and QS ) 0.95-1.1 mm/s. [135][136][137]189 Ayyub et al further reported that the RT Mo ¨ssbauer spectrum of the amorphous Fe 2 O 3 contains an additional singlet component (IS Fe ) 0.12-0.16 mm/s), constituting approximately 25% of the overall area of the spectrum. 135 The origin of this singlet still remains unexplained.…”

Section: Fe 2 O 3 Formed During the Thermal Decomposition Of β-Feo(oh...mentioning

confidence: 99%

Iron(III) Oxides from Thermal ProcessesSynthesis, Structural and Magnetic Properties, Mössbauer Spectroscopy Characterization, and Applications

2002

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Structural and magnetic properties, methods of synthesis, and applications of seven iron-(III) oxide polymorphs, including rare beta, epsilon, amorphous, and high-pressure forms, are reviewed. Thermal transformations resulting in the formation of iron oxides are classified according to different parameters, and their mechanisms are discussed. 57 Fe Mo ¨ssbauer spectroscopy is presented as a powerful tool for the identification, distinction, and characterization of individual polymorphs. The advantages of Mo ¨ssbauer spectroscopy are demonstrated with two examples related to the study of the thermally induced solid-state reactions of Fe 2 (SO 4 ) 3 . Lead-InIron(III) oxide is not only a strategic industrial material but also a convenient compound for the general study of the polymorphism and the mutual polymorphous changes in nanoparticles. The existence of amorphous Fe 2 O 3 and four polymorphs (alpha, beta, gamma, and epsilon) has been established. Their discoveries as well as the majority of formation processes are connected with thermal transformations of iron-bearing materials in an oxidizing atmosphere. 57 Fe Mo ¨ssbauer spectroscopy is a unique method that allows one to distinguish and identify individual structural forms, amorphous and nanostructured Fe 2 O 3 particles, to analyze their magnetic properties and to study their formation mechanism during thermally induced solidstate reactions. In this review, thermal processes resulted in the Fe 2 O 3 formation are classified from different viewpoints and their mechanism is discussed. Applications, structural and magnetic properties, and methods of synthesis of all known forms of iron(III) oxide and their Mo ¨ssbauer characterization are also summarized. A detailed survey of the properties of rare forms (amorphous Fe 2 O 3 , β-Fe 2 O 3 , -Fe 2 O 3 , and highpressure Fe 2 O 3 ) is presented for the first time. With respect to the more known R-Fe 2 O 3 and γ-Fe 2 O 3 , the presented data spring from a series of previous works, including the excellent book by R. M. Cornell and U. Schwertmann. 1 Some unresolved problems, such as the relation between the properties of the original ferrogenous precursor and the structure of the formed iron-(III) oxide, or the experimental possibility to distinguish the amorphous Fe 2 O 3 from nanostructured γ-Fe 2 O 3 or R-Fe 2 O 3 particles are discussed. The value of Mo ¨ssbauer spectroscopy for the characterization of iron(III) oxides produced by thermal processes is demonstrated with two experimental examples taken from our work in the field. † Dedicated to R. L. Mo ¨ssbauer on the occasion of the 40 th jubilee of Nobel Prize presentation.

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“…7,39 Amorphous Fe 2 O 3 phase in the form of powder, thin film, or nanocomposite was prepared by several routes including sonochemical, precipitation, sol-gel, decomposition, or deposition methods. [40][41][42][43][44][45][46][47][48][49][50][51] The thermally induced solid-state decompositions of iron-containing materials represent an important group of the preparation methods. 1,34,[52][53][54][55] However, some solid-state reactions result in the simultaneous formation of different polymorphs under any particular reaction conditions.…”

Section: Introductionmentioning

confidence: 99%

Iron(III) Oxide Nanoparticles in the Thermally Induced Oxidative Decomposition of Prussian Blue, Fe₄[Fe(CN)₆]₃

Zbořil

Machala

Mashlan

et al. 2004

Crystal Growth & Design

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The thermally induced decomposition of Prussian Blue, Fe 4 [Fe(CN) 6 ] 3 (PB), was studied in air at 250 and 350 °C. Amorphous Fe 2 O 3 nanoparticles, cubic bixbyite β-and cubic spinel γ-Fe 2 O 3 (maghemite) polymorphs, have been identified as the products of the decomposition under different reaction conditions. 57 Fe Mo ¨ssbauer spectroscopy, XRD, AFM, TEM, quasielastic light scattering method (QELS) of particle size analysis, BET surface area, and magnetization measurements were used to understand the influence of the PB particle size and oxidation conditions on the decomposition mechanism at 250 and 350 °C. At a minimum decomposition temperature of 250 °C, amorphous Fe 2 O 3 nanoparticles were formed with the size ranging from 1 to 4 nm and large surface area of 400-200 m 2 /g in dependence on the PB particle size. Such small amorphous Fe 2 O 3 nanoparticles were obtained by the solid-state route for the first time. At 350 °C, cubic β-Fe 2 O 3 and γ-Fe 2 O 3 polymorphs were identified and their contents were found to be strongly dependent on the initial PB particle size and oxidation-diffusion conditions. Generally, the higher relative content of γ-Fe 2 O 3 was obtained for larger PB particles and in air-limited conditions.

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An amorphous magnetically ordered ultra-thin film of Fe2O3 on graphite: Mössbauer spectroscopy

Cited by 13 publications

References 10 publications

Magnetism of amorphous Fe ₂ O ₃ nanopowders synthesized by solid‐state reactions

Magnetism of amorphous Fe ₂ O ₃ nanopowders synthesized by solid‐state reactions

Iron(III) Oxides from Thermal ProcessesSynthesis, Structural and Magnetic Properties, Mössbauer Spectroscopy Characterization, and Applications

Iron(III) Oxide Nanoparticles in the Thermally Induced Oxidative Decomposition of Prussian Blue, Fe₄[Fe(CN)₆]₃

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An amorphous magnetically ordered ultra-thin film of Fe2O3 on graphite: Mössbauer spectroscopy

Cited by 13 publications

References 10 publications

Magnetism of amorphous Fe 2 O 3 nanopowders synthesized by solid‐state reactions

Magnetism of amorphous Fe 2 O 3 nanopowders synthesized by solid‐state reactions

Iron(III) Oxides from Thermal ProcessesSynthesis, Structural and Magnetic Properties, Mössbauer Spectroscopy Characterization, and Applications

Iron(III) Oxide Nanoparticles in the Thermally Induced Oxidative Decomposition of Prussian Blue, Fe4[Fe(CN)6]3

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Magnetism of amorphous Fe ₂ O ₃ nanopowders synthesized by solid‐state reactions

Magnetism of amorphous Fe ₂ O ₃ nanopowders synthesized by solid‐state reactions

Iron(III) Oxide Nanoparticles in the Thermally Induced Oxidative Decomposition of Prussian Blue, Fe₄[Fe(CN)₆]₃