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Effect of Dipolar and Exchange Interactions on Magnetic Blocking of Maghemite Nanoparticles by K. Nadeem; H. Krenn; T. Traussnig; R. Würschum; D.V. Szabó; I. Letofsky-Papst is a Materials Science article available to read on EtoBox.

What is Effect of Dipolar and Exchange Interactions on Magnetic Blocking of Maghemite Nanoparticles about?

Magnetic interparticle interactions compete with the magnetic blocking of ultrafine magnetic nanoparticles. We have prepared maghemite (g-Fe 2 O 3 ) nanoparticles by microwave plasma synthesis as a loose powder and in compacted form. In ZFC/FC measurements, blocking temperature of the compacted sample C is larger than that of the powder sample P. The frequency dependence of AC susceptibility of the sample C shows a large shift of blocking temperature with increasing frequency. Vogel-Fulcher law gives a large value of T 0 for the sample C. To get evidence of a possible spin-glass freezing in both samples, scaling law fitting is applied to the AC susceptibility data. The value of the exponent (zv) of the critical slowing down dynamics fits to the spin-glass regime for both samples. For the sample P, spin-glass freezing occurs on the surface of individual nanoparticles, while in the sample C surface spin-glass freezing is concomitant with a superspin-glass formation as a consequence of coupling between particles. The sample C also shows an enhancement of coercivity due to dipolar interactions among the nanoparticles. Exchange interactions are attributed only to touching nanoparticles

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Author

K. Nadeem; H. Krenn; T. Traussnig; R. Würschum; D.V. Szabó; I. Letofsky-Papst

Publisher

Elsevier Science; Elsevier ; Elsevier BV (ISSN 0304-8853)

Published

2011

Language

EN

Field

Materials Science (Physical Sciences)