Shifts in blocking temperature spectra for magnetite powders as a function of grain size and applied magnetic field

Clauter, Dean A.; Schmidt, Victor A.

doi:10.1016/0031-9201(81)90100-x

Cited by 12 publications

(6 citation statements)

References 6 publications

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“…The unblocking spectrum of high field TRM, containing as it does both thermally and isothermally blocked components, extends down to room temperature. These data are similar to the field dependence of blocking temperature spectra of monodomain magnetite, determined by Sugiura (1980) and Clauter & Schmidt (1981).…”

Section: T H E S T a B I L I T Y O F T R Msupporting

confidence: 85%

An experimental study of the intensity and stability of thermoremanent magnetization acquired by synthetic monodomain titanomagnetite substituted by aluminium

Özdemir

O’Reilly

1982

Geophysical Journal International

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Titanomagnetites of composition Fe,.,-6Al6 Ti0.604 and A16Ti,,04(6 =0, 0.1 and 0.2 in both cases) were prepared in the monodomain state by pulverization of sintered synthetic material. In low fields, the thermoremanence (TRM) was found to be linear with inducing field and of high enough intensity to account for typical natural remanent magnetizations of fresh submarine basalts. The higher field TRM acquisition curves follow the NBel model curve for an assemblage of non-interacting identical particles in a general way only, the differences being due t o interactions, or the range of particle blocking temperatures and volumes or other features of the samples not included in the model. The unblocking temperatures of low field TRM lie in a narrow range below the Curie point. The low field TRM is very resistant to alternating field demagnetization and provides a very striking illustration of the strength of the TRM mechanism in preserving a stable record of a weak magnetic field. The result of a Lowrie-Fuller test on the material is consistent with the monodomain state.

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Section: T H E S T a B I L I T Y O F T R Msupporting

confidence: 85%

An experimental study of the intensity and stability of thermoremanent magnetization acquired by synthetic monodomain titanomagnetite substituted by aluminium

Özdemir

O’Reilly

1982

Geophysical Journal International

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“…Unfortunately this approach has not led to the anticipated clearcut re. sult [Dunlop and West, 1969;Dunlop and Waddington, 1975;Day, 1977; Tucker and O'Reilly, 1980'1, the agreement between the data and either theory being a good deal less convincing than the matches found in the present paper.…”

Section: Demonstrate That the Experimental Dependence Of He On T (Orcontrasting

confidence: 70%

“…His theoretical-type curves indicated rather similar dependences for single-domain (SD) grains with thermally activated magnetization reversal and for small multidomain (MD) grains with nonthermally activated domain wall motion, provided similar values for microscopic coercive force H• were assumed in the two cases. Sugiura [1980] and Wohlfarth [1980] have reported elegant experimental tests of the SD predictions INkel, 1949], using SD magnetite and a variety of spin glass materials respectively, while Clauter and Schmidt [1981] have examined the variation of TB with internal as well as applied fields.…”

Section: Introductionmentioning

confidence: 99%

Field dependence of magnetic blocking temperature: Analog tests using coercive force data

Dunlop¹

1982

J. Geophys. Res.

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The field dependence of blocking temperature TB and the temperature dependence of coercive force Hc are shown to be analogous functions. Coercive force data, obtained routinely with standard equipment, can therefore be used in analog tests of theories of thermoremanent magnetization (TRM). Analog Hc data reported in this paper for single‐domain and small multidomain magnetite dispersions and a variety of rocks are matched equally well by Néel's (1949) theory of thermally activated magnetization changes or Néel's (1955) theory of field‐induced domain wall displacements. The temperature dependence of domain wall pinning is a crucial unknown in the wall displacement model, allowing considerable latitude in curve fitting. If the thermal activation model is assumed, reasonable values are found for the volume activated in a single magnetization reversal or wall jump in the fine‐ and medium‐grained rocks tested. Additional independent evidence from hysteresis and microscopic examination is necessary, however, to choose between the competing TRM models in individual cases.

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“…Nevertheless, the observed independence of the blocking temperature on the particle size of amorphous Fe 2 O 3 powders seems to be a special case probably related with the strength of interaction among particles, because this phenomenon is rarely described in literature. The majority of nanopowdered systems reveal an increase in blocking temperature with particle size [23][24][25][26]. Only Goya et al registered a similar independence of the blocking temperature on the particle size for CuFe 2 O 4 nanopowders prepared by high-energy ball milling [27].…”

Section: Resultsmentioning

confidence: 89%

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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Shifts in blocking temperature spectra for magnetite powders as a function of grain size and applied magnetic field

Cited by 12 publications

References 6 publications

An experimental study of the intensity and stability of thermoremanent magnetization acquired by synthetic monodomain titanomagnetite substituted by aluminium

An experimental study of the intensity and stability of thermoremanent magnetization acquired by synthetic monodomain titanomagnetite substituted by aluminium

Field dependence of magnetic blocking temperature: Analog tests using coercive force data

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

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Shifts in blocking temperature spectra for magnetite powders as a function of grain size and applied magnetic field

Cited by 12 publications

References 6 publications

An experimental study of the intensity and stability of thermoremanent magnetization acquired by synthetic monodomain titanomagnetite substituted by aluminium

An experimental study of the intensity and stability of thermoremanent magnetization acquired by synthetic monodomain titanomagnetite substituted by aluminium

Field dependence of magnetic blocking temperature: Analog tests using coercive force data

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

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