Spin correlation, excitation, and relaxation of antiferromagnetic hematite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>α</mml:mi><mml:mtext>−</mml:mtext><mml:msub><mml:mi mathvariant="normal">Fe</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>nanoparticles

Optically induced ultrafast demagnetization and its recovery in superparamagnetic colloidal iron oxide (Fe3O4) nanocrystals have been investigated via time-resolved Faraday rotation measurements. Optical excitation with near-infrared laser pulse resulted in ultrafast demagnetization in approximately 100 fs via the destruction of ferrimagnetic ordering. The degree of demagnetization increased with the excitation density, and the complete demagnetization reached at approximately 10% excitation density. The magnetization recovered on two time scales, several picoseconds and hundreds of picoseconds, which can be associated with the initial reestablishment of the ferrimagnetic ordering and the electronic relaxation back to the ground state, respectively. The amplitude of the slower recovery component increased with the size of the nanocrystals, suggesting the size-dependent ferrimagnetic ordering throughout the volume of the nanocrystal.

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Neutron study of magnetic excitations in8−nmα−Fe2O3
Kuhn
¹
,
Lefmann
²
,
Bahl
³

et al. 2006
Phys. Rev. B
30
6
23
0
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By use of inelastic neutron scattering we have studied magnetic fluctuations in 8-nm particles of antiferromagnetic ␣-Fe 2 O 3 ͑hematite͒ as a function of temperature and applied magnetic fields. The fluctuations are dominated by uniform excitations. Studies have been performed on both coated ͑noninteracting͒ and uncoated ͑interacting͒ particles. We have estimated the magnetic anisotropy energy and found that the data are in good agreement with the value obtained from Mössbauer spectroscopy. The energy 0 of the uniform excitations depends strongly on the uncompensated moment, which is caused by finite-size effects, and we have estimated the size of this moment from the experimental neutron data. The field dependence of 0 for the interacting nanoparticles differs strongly from that of the noninteracting nanoparticles, and this is a result of the influence of exchange interaction between the particles.

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Spin correlation, excitation, and relaxation of antiferromagnetic hematiteα−Fe2O3nanoparticles

Cited by 4 publications

References 19 publications

Size and anisotropy effects on magnetic properties of antiferromagnetic nanoparticles

Size and anisotropy effects on magnetic properties of antiferromagnetic nanoparticles

Size-Dependent Ultrafast Magnetization Dynamics in Iron Oxide (Fe₃O₄) Nanocrystals

Neutron study of magnetic excitations in8−nmα−Fe2O3
Kuhn
¹
,
Lefmann
²
,
Bahl
³

et al. 2006
Phys. Rev. B
30
6
23
0
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Spin correlation, excitation, and relaxation of antiferromagnetic hematiteα−Fe2O3nanoparticles

Cited by 4 publications

References 19 publications

Size and anisotropy effects on magnetic properties of antiferromagnetic nanoparticles

Size and anisotropy effects on magnetic properties of antiferromagnetic nanoparticles

Size-Dependent Ultrafast Magnetization Dynamics in Iron Oxide (Fe3O4) Nanocrystals

Neutron study of magnetic excitations in8−nmα−Fe2O3Kuhn1, Lefmann2, Bahl3 et al. 2006Phys. Rev. B306230View full textAdd to dashboardCite

Contact Info

Product

Resources

About

Size-Dependent Ultrafast Magnetization Dynamics in Iron Oxide (Fe₃O₄) Nanocrystals

Neutron study of magnetic excitations in8−nmα−Fe2O3
Kuhn
¹
,
Lefmann
²
,
Bahl
³

et al. 2006
Phys. Rev. B
30
6
23
0
View full text Add to dashboard Cite