Abstract

MnFe₂O₄ nanoparticles with diameters ranging from about 4 to 50 nm were synthesized using a modified coprecipitation method. X-ray diffractograms revealed a pure phase spinel ferrite structure for all samples. Transmission electron microscopy showed that the particles consist of a mixture of both spherical (smaller) and cubic (larger) particles dictated by the reaction kinetics. The Néel temperatures (TN) of MnFe₂O₄ for various particle sizes were determined by using high temperature magnetometry. The ∽4 nm MnFe₂O₄ particles showed a TN of about 320°C whereas the ∽50 nm particles had a TN of about 400°C. The high Neel temperature, compared with the bulk MnFe₂O₄ TN of 300°C, is due to a change in cation distribution between the tetrahedral and octahedral sites of the spinel lattice. Results of extended x-ray absorption fine structure measurements indicate a systematic change in the cation distribution dependent on processing conditions.

Notes

Originally published in Journal of Applied Physics 101, 09M509 (2007). DOI:10.1063/1.2710218 (http://dx.doi.org/10.1063/1.2710218).

Keywords

processing conditions, cation inversion, chemically synthesized MnFe₂O₄, pure phase spinel ferrite structure, Néel temperatures, TN

Subject Categories

Nanoparticles, Magnetic properties, Extended X-ray absorption fine structure

Disciplines

Electromagnetics and photonics

Publisher

American Institute of Physics

Publication Date

5-1-2007

Rights Information

Copyright 2007 American Institute of Physics.

Rights Holder

American Institute of Physics

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size_dependent_magnetic_fig1.zip (1017 kB)
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size_dependent_magnetic_fig2.zip (110 kB)
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size_dependent_magnetic_fig1.zip (1017 kB)
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size_dependent_magnetic_fig2.zip (110 kB)
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size_dependent_magnetic_fig3.zip (32 kB)
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