Low-temperature stable nanometer-size fcc-Fe particles with no magnetic ordering

Haneda, K.; Zhou, Zhimou; Morrish, A. H.; Majima, Tetsuro; Miyahara, T.

doi:10.1103/physrevb.46.13832

Cited by 71 publications

(35 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is worth noting that nano-onion morphology proposed is different respect to other nanoparticulate systems that found ␣-Fe core surrounded by a shell of ␥-Fe. 41,50 On the other hand, the random dispersion of Fe-NPs through the carbon matrix makes them being close to each other or sometimes even into contact ͓see Figs. 1͑c͒ and 8͑a͔͒.…”

Section: Discussionmentioning

confidence: 99%

“…59,60 Some studies on FCC-Fe films found AFM response below 80 K ͑Ref. 53͒ while others assured that magnetic ordering occurs at around 65 K. 61 On the contrary other exhaustive studies from 57 Fe Mössbauer spectrometry on FCC-Fe particles show that they behave as paramagnets at least down to 1.8 K. 50 On the other hand, several studies on carbon nanotubes reveal that FCC-Fe NPs undergo an AFM transition around 80-100 K. 41,42 Therefore, the formation of considerable amount of ␥-Fe phase in Fe-NP systems open new possibilities for the study of the striking magnetism of ␥-Fe. The reason for the stabilization of the ␥-Fe phase at room temperature is unclear.…”

Section: Introductionmentioning

confidence: 99%

“…Up to now, this ␥-Fe phase was observed in small iron precipitates embedded in a Cu matrix, 38 in FeCu mechanically alloyed compounds, 39,40 in the synthesis of carbon nanotubes, [41][42][43][44][45][46][47][48] or in Fe-NPs and thin films but confined down to a few monolayers of thickness. [49][50][51][52][53][54][55] The magnetism of ␥-Fe phase depends strongly on the Fe-Fe interatomic distances 56 although both the morphology of the sample and the particle size could play an important role. Indeed, AFM interactions are favored at low temperatures ͑T Ͻ 100 K͒ and for lattice parameters, a Ͻ 3.6 Å, while FM state with high Fe magnetic moment values ͑ Ͼ 2.5 B ͒ can be stabilized for a Ͼ 3.6 Å.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Microstructure and magnetism of nanoparticles withγ-Fecore surrounded byα-Feand iron oxide shells

et al. 2010

View full text Add to dashboard Cite

Iron-carbon nanocomposites have been elaborated by means of a simple chemical procedure based on in situ synthesis of iron nanoparticles within the nanopores of an activated carbon. The Fe nanoparticles present a broad particle-size distribution ͑5-40 nm͒. A combined structural and magnetic study seems to suggest that most of the nanoparticles of mean size ϳ15 nm have exotic "onionlike" core-shell morphology of ␥-Fe nucleus surrounded by a concentric double shell of ␣-Fe and maghemitelike oxide. The true nature of Fe-oxide was successfully evidenced through room temperature x-ray absorption spectroscopy. The whole system does not reach a fully superparamagnetic regime even at 750 K, probably due to higher blocking temperatures for the largest nanoparticles. Mössbauer spectrometry indicates that low temperature para-to-antiferromagnetic transition for the ␥-Fe phase cannot be discarded. In addition, the external Fe-oxide shell exhibits spin-glass behavior giving rise to the freezing of its magnetic moments at low temperatures. Hence, we propose a competing double magnetic coupling: ͑i͒ the oxide shell/␣-Fe interaction and ͑ii͒ the possible antiferromagnetic coupling between ␥-Fe nucleus and ␣-Fe layer; as being both responsible for the observed exchange bias effect at T =5 K ͑H ex Ϸ 150 Oe͒.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Microstructure and magnetism of nanoparticles withγ-Fecore surrounded byα-Feand iron oxide shells

et al. 2010

View full text Add to dashboard Cite

show abstract

“…It has a similar amount of Fe 2+ cations as the Prp 36 Alm 64 sample, but the decomposition process was quite different. From the XRD pattern of the sample heated up to 1120 °C, it is possible to see that decomposition has already started and the phases identified are: -Fe, hercynite, tephroite ((Mn,Fe)SiO 4 ), quartz (SiO 2 ), and the original garnet (92.8%).…”

Section: Samples With Intermediate Composition: Prp-alm and Sps-alm Smentioning

confidence: 98%

“…Together with the information on the phase composition, it was possible to suggest a relationship between the phases formed after Prp 36 …”

Section: Samples With Intermediate Composition: Prp-alm and Sps-alm Smentioning

confidence: 99%

The influence of the iron content on the reductive decomposition of A3−xFexAl2Si3O12 garnets (A = Mg, Mn; 0.47 ≤ x ≤ 2.85)

Aparicio¹,

Filip²,

Mashlan³

et al. 2014

AIP Conference Proceedings

View full text Add to dashboard Cite

Abstract. Thermally-induced reductive decomposition of natural iron-bearing garnets of the almandine-pyrope and almandine-spessartine series were studied at temperatures up to 1200 °C (heating rate of 10 °C/min) under atmosphere of forming gas (10% of H 2 in N 2 ). Crystallochemical formula of the studied garnet was calculated as VIII (A 3-x Fe 2+x ) VI (Al, Fe 3+ ) 2 Si 3 O 12 , where the amount of Fe 3+ in the octahedral sites is negligible with the exception of pyrope, A = Mg, Mn, and 0.47 x 2.85. The observed decomposition temperature, determined from differential scanning calorimetry and thermogravimetry, is greater than 1000 °C in all cases and showed almost linear dependence on the iron content in the dodecahedral sites of the studied garnets, with the exception of garnet with a near-pyrope composition (Prp 80 Alm 20 ). The initial garnet samples and decomposition products were characterized in details by means of X-ray powder diffraction and 57 Fe Mössbauer spectroscopy. We found that all studied garnets have common decomposition products such as metallic iron (in general, rounded particles below 4 μm) and Fe-spinel; the other identified decomposition products depend on starting chemical composition of the garnet: Fe-cordierite, olivine (fayalite or tephroite), cristobalite, pyroxene (enstatite or pigeonite), and anorthite. Anorthite and pigeonite were only present in garnets with Ca in the dodecahedral site. All the identified phases were usually well crystallized.

show abstract

Introduction

Губин

2009

Magnetic Nanoparticles

View full text Add to dashboard Cite

Low-temperature stable nanometer-size fcc-Fe particles with no magnetic ordering

Cited by 71 publications

References 41 publications

Microstructure and magnetism of nanoparticles withγ-Fecore surrounded byα-Feand iron oxide shells

Microstructure and magnetism of nanoparticles withγ-Fecore surrounded byα-Feand iron oxide shells

The influence of the iron content on the reductive decomposition of A3−xFexAl2Si3O12 garnets (A = Mg, Mn; 0.47 ≤ x ≤ 2.85)

Introduction

Contact Info

Product

Resources

About