Specific heat of Fe3O4−xFx in the neighbourhood of the verwey temperature (with x=0, 0.1 and 0.25)

Rigo, M. O.; Kleinclauss, J.; Pointon, A. J.

doi:10.1016/0038-1098(78)90661-0

Cited by 16 publications

(3 citation statements)

References 20 publications

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“…(v) Evidently, owing to these uncertainties, resulting from (i) lack of perfect crystals and (ii) absence of reliable quality control, it would be unrealistic to expect the definite solution of the magnetite problem during era (II). (a) Multi-stage transitions in the neighbourhood of T v have been reported from specific heat [79][80][81][82][83][84] and spontaneous magnetization in combination with Mössbauer-effect measurements [85][86][87][88]. Whereas in early specific heat investigations only one single anomaly, somewhat below 120 K, had been observed [19][20][21][22], later on the appearance of double peaks (pronounced bifurcation) near 113 and 119 K have been reported by Westrum et al [79][80][81] [NSC/SSC, 119 K], Matsui et al [82] [SSC, 118.4 K] and Rigo et al [83,84] [SSC, powder, 123 K].…”

Section: Experiments In Era (Ii)mentioning

confidence: 99%

“…(a) Multi-stage transitions in the neighbourhood of T v have been reported from specific heat [79][80][81][82][83][84] and spontaneous magnetization in combination with Mössbauer-effect measurements [85][86][87][88]. Whereas in early specific heat investigations only one single anomaly, somewhat below 120 K, had been observed [19][20][21][22], later on the appearance of double peaks (pronounced bifurcation) near 113 and 119 K have been reported by Westrum et al [79][80][81] [NSC/SSC, 119 K], Matsui et al [82] [SSC, 118.4 K] and Rigo et al [83,84] [SSC, powder, 123 K]. For some time the phenomenon of a multi-stage-type Verwey transition has been under serious discussion, even more since Hirsch et al [85][86][87][88] [SPC, 116.6 K], too, promoted the idea of an extended multi-stage transition, composed of up to 12 stages within the temperature range 15 K < T < 151 K (!)…”

Section: Experiments In Era (Ii)mentioning

confidence: 99%

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The Verwey transition - a topical review

Walz¹

2002

J. Phys.: Condens. Matter

698

663

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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: Experiments In Era (Ii)mentioning

confidence: 99%

Section: Experiments In Era (Ii)mentioning

confidence: 99%

The Verwey transition - a topical review

Walz¹

2002

J. Phys.: Condens. Matter

698

663

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“…For one of these samples neutron scattering experiments show that the heat capacity anomaly a t lower temperatures occurring a t 110.6 K (higher-temperature peak a t 119 K) is associated with a lattice transformation [39]. However, upon addition of certain concentrations of dopants (Cd or Zn) the bifurcation disappears and a single transition was observed in the heat capacity of the doped sample a t temperatures below 115 K [40] and in natural magnetite at 117.3 K. The specific heat of fluorine-doped (0.1 to 0.25%) sintered Fe,O, samples show only a single peak a t different temperatures, between 114 and 122 K [41]. Recently systematic investigation on stressed, stress-released but unannealed, and annealed pure synthetic Fe,O,, grown by Bridgman's method, prove that the presence of residual stresses lowers the Verwey temperature considerably (from 117.2 to 108 K), broadens the temperature width of the anomaly, and produces a twin peak fitructure in the heat capacity (31.…”

Section: Introductionmentioning

confidence: 99%

Vacancy Effect on the Transition Temperature of Magnetite

Gmelin

Lenge

Kronmüller

1983

Phys. Stat. Sol. (a)

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The specific heat of magnetite (Fe3O4) is measured from 5 to 130 K for two single crystals and near the Verwey transition temperature Tv (110 K ≤ T ≦ 130 K) for various polycrystalline samples. The data are compared to the large number of previous measurements. It is observed that the presence of vacancies in undoped Fe3O4 plays a dominant role in lowering and broadening Tv and diminishing ΔH. One of the single crystals has an entropy change of 6.24 J/K mol at Tv = 123.6 K (ΔH = 770 J/mol), which ie among the highest values observed up to date. It is concluded furthermore that in pure magnetite there exists only one anomaly in the low temperature specific heat Cp (1.5 K ≦ T ≦ 300 K) : the Verwey transition at Tv = 124 K, which is displayed by a single peak in Cp. This result is in contrast to numerous earlier measurements.

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The Verwey Transition in Polycrystalline Cobalt-Iron Ferrites

Abellán

Ortuño

1986

phys. stat. sol. (a)

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The Verwey transition is analyzed by measuring the initial permeability as a function of tempera‐ture in polycrystalline CoxFe3‐xO4 (with 0 ≦ x ≦ 0.04). The transition temperature slightly decreases with cobalt concentration. A small impurity concentration (≦ 5%) is sufficient to wipe out any sign of the transition. Most samples show a marked thermal hysteresis between heating and cooling curves above the transition.

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Specific heat of Fe3O4−xFx in the neighbourhood of the verwey temperature (with x=0, 0.1 and 0.25)

Cited by 16 publications

References 20 publications

The Verwey transition - a topical review

The Verwey transition - a topical review

Vacancy Effect on the Transition Temperature of Magnetite

The Verwey Transition in Polycrystalline Cobalt-Iron Ferrites

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