| Autor: |
Raikher, Yu. L., Stepanov, V. I., Depeyrot, J., Sousa, M. H., Tourinho, F. A., Hasmonay, E., Perzynski, R. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 11/1/2004, Vol. 96 Issue 9, p5226-5233, 8p, 1 Diagram, 4 Graphs |
| Abstrakt: |
Field dependence of dynamic magneto-orientational birefringence in a ferrocolloid based on the nickel-ferrite nanoparticles is examined. The nanoparticles are electrostatically stabilized and suspended in glycerin at low-volume fractions [uppercase_phi_synonym]<=0.75%. The colloids are tested under crossed magnetic fields: an alternating weak (probing) and a constant strong (bias) one. By comparison to a theoretical model of the birefringence relaxation, an evaluation of the mean nanoparticle magnetic anisotropy energy, Ea, is done. We get σ=Ea/kT∼10, given that the particles are rather polydisperse: a log-normal distribution with exp[〈ln d〉]=6.5 nm and the width s=0.55. With the parameter σ in such a range, the NiFe2O4 grains make a first example of a nanodisperse material (ferrofluid) whose anisotropy properties differ substantially from both magnetically soft (e.g., maghemite with σ<2) and magnetically hard (e.g., cobalt ferrite with σ>50) nanosubstances of the same grain size. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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