Specific heat of magnetite near the Verwey transition Is there more than one phase transition?

Gmelin, E.; Lenge, N.; Kronüller, H.

doi:10.1080/13642818408238856

Cited by 16 publications

(6 citation statements)

References 9 publications

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“…Our MAE analysis revealed significant deviations between the spectra of the powdered and perfect crystals which could be unambiguously associated with the presence of internal stresses and B-type vacancies which had been introduced during the powdering process [184]. On the occasion of this test we were also able to finally exclude, as had already been done previously [185], the occurrence of a further, long-debated anomaly at 10 K [172,[179][180][181][182][183], which initially had been reported by Todo et al [186]. These final MAE results have been confirmed by further specific heat investigations performed since then [187,188].…”

Section: Elimination Of Multi-stage (N >supporting

confidence: 53%

“…[82] clear results concerning this problem, cf section 3.2.2, the relevance of a second peak near 110 K, besides the major one at T v , remained under discussion for many further years. Whereas Rigo et al [84,179,180] regarded this second peak-obtained on powdered material-as purely intrinsic, Gmelin et al [181,182] and Shepherd et al [183], on well prepared single crystals, could not detect any trace of this 110 K anomaly. The final 'knockout' for the thermal bifurcation, as an intrisic process of perfect magnetite, was accomplished by means of the MAE [184].…”

Section: Elimination Of Multi-stage (N >mentioning

confidence: 95%

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The Verwey transition - a topical review

Walz¹

2002

J. Phys.: Condens. Matter

700

651

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This review encompasses the story of the Verwey transition in magnetite over a period of about 90 years, from its discovery up to the present. Despite this long period of thorough investigation, the intricate multi-particle system Fe3O4 with its various magneto-electronic interactions is not completely understood, as yet - although considerable progress has been achieved, especially during the last two decades. It therefore appeared appropriate to subdivide this retrospect into three eras: (I) from the detection of the effect to the Verwey model (1913-1947), being followed by a period of: (II) checking, questioning and modification of Verwey's original concepts (1947-1979). Owing to prevailing under-estimation of the role of crystal preparation and qualitiy control, this period is also characterized by a series of uncertainties and erroneous statements concerning the reaction order (one or two) and type of the transition (multi-stage or single stage). These latter problems, beyond others, could definitely be solved within era (III) (1979 to the present) - in favour of a first-order, single-stage transition near 125 K - on the basis of experimental and theoretical standards established in the course of a most inspiring conference organized in 1979 by Sir Nevill Mott in Cambridge and solely devoted to the present topic. Regarding the experimental field of further research, the remarkable efficiency of magnetic after-effect (MAE) spectroscopy as a sensitive probe for quality control and investigation of low-temperature (4 KTv) into a Wigner crystal (T

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Section: Elimination Of Multi-stage (N >supporting

confidence: 53%

Section: Elimination Of Multi-stage (N >mentioning

confidence: 95%

The Verwey transition - a topical review

Walz¹

2002

J. Phys.: Condens. Matter

700

651

View full text Add to dashboard Cite

show abstract

“…Figure 2: Energy separation due to Jahn-Teller distortion (up) and depiction of trimeron concept in single Fe +2 O 6 octahedra (down) (a) [8]. Changes in magnetic susceptibility, resistance, and specific heat at T V (b) [10,17]. For clarity, the temperature scale for R and χ′ was shifted concerning the true temperature scale.…”

Section: Spin Downmentioning

confidence: 99%

“…Fe 3 O 4 is a cubic ferrimagnetic oxide with the highest magnetization M = 4 2 μ B below Curie temperature, T C = 858 K. Band structure calculations predict half-metallic (-100% spin polarization) character of Fe 3 O 4 with room temperature conductivity, σ = 200 (Ω•cm) -1 [8,9]. Stoichiometric Fe 3 O 4 shows VT wherein first-order structural phase transformation occurs around 124 K (T V ) [10]. In the lowtemperature phase, Fe 3 O 4 is an insulator, has a monoclinic structure connected to the charge ordering, and exhibits an orbital order on the Fe 2+ sites [11].…”

Section: Introductionmentioning

confidence: 99%

A Short Review on Verwey Transition in Nanostructured Fe₃O₄ Materials

Bohra

Agarwal

Singh

2019

Journal of Nanomaterials

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Verwey transition (VT) of Fe3O4 has been extensively investigated as this results in sharp changes in its physical properties. Exploitation of VT for potential applications in spin/charge transport, multiferroicity, exchange bias, and spin Seebeck effect-based devices has attracted researchers recently. Although hundreds of reports have been published, the origin of VT is still debatable. Besides, not only the size effects have a significant impact on VT in Fe3O4, even the conditions of synthesis of Fe3O4 nanostructures mostly affect the changes in VT. Here, we review not only the effects of scaling but also the growth conditions of the Fe3O4 nanostructures on the VT and their novel applications in spintronics and nanotechnology.

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“…[8][9][10] The Verwey transition 11 typically appears as an anomaly appears in the heat capacity around T ) 120 K (T v ). Some controversy surrounds the exact shape of the heat capacity peak; some authors report a single peak [12][13][14] in this region, while others have observed two or more. 11,[15][16][17] In those papers that report multiple peaks, there is no consistency in the peak separation or peak shape.…”

Section: Introductionmentioning

confidence: 99%

Heat Capacity Studies of Nanocrystalline Magnetite (Fe₃O₄)

et al. 2010

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The Verwey transition in magnetite (Fe 3 O 4 ) has been studied extensively with a wide assortment of experimental techniques to investigate the effects of impurities, oxygen stoichiometry, and crystal quality; however, no studies have tested the effects of crystal size on the Verwey transition. In this study, the heat capacity of a magnetite powder with an average crystallite size of 13 nm was measured in the temperature range of 0.5-350 K. No obvious anomaly was observed in the heat capacity in the vicinity of 120 K, yet the measurements exhibited unusual thermal behaviors between 50 and 90 K with relaxation times increasing from an average of 25 min to as much as 5 h in this temperature interval. The behavior is typical of a phase transition, so the lack of a distinct anomaly suggests either the phenomenon is spread out over a large temperature interval with little enthalpy or an insulating phase with different thermal conductivities appears. The heat capacity below 90 K was dependent on cooling rate with an inconsistent anomaly found below 4 K. The results suggest that the Verwey transition has a particle-size dependence. Additionally, theoretical fits below 15 K suggest that magnetite nanoparticles display anisotropic ferrimagnetic behavior and a superparamagnetic contribution to the heat capacity which are properties not observed in bulk magnetite.

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Specific heat of magnetite near the Verwey transition Is there more than one phase transition?

Cited by 16 publications

References 9 publications

The Verwey transition - a topical review

The Verwey transition - a topical review

A Short Review on Verwey Transition in Nanostructured Fe₃O₄ Materials

Heat Capacity Studies of Nanocrystalline Magnetite (Fe₃O₄)

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Specific heat of magnetite near the Verwey transition Is there more than one phase transition?

Cited by 16 publications

References 9 publications

The Verwey transition - a topical review

The Verwey transition - a topical review

A Short Review on Verwey Transition in Nanostructured Fe3O4 Materials

Heat Capacity Studies of Nanocrystalline Magnetite (Fe3O4)

Contact Info

Product

Resources

About

A Short Review on Verwey Transition in Nanostructured Fe₃O₄ Materials

Heat Capacity Studies of Nanocrystalline Magnetite (Fe₃O₄)