Magnetic behavior of Fe:Al2O3 nanocomposite films produced by pulsed laser deposition

N. M. Dempsey*, L. Ranno, D. Givord, J. Gonzalo, R. Serna, G. T. Fei, A. K. Petford-Long, R. C. Doole, D. E. Hole

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

Structured nanocomposite films consisting of five Fe layers embedded in an amorphous Al2O3 matrix (Fe:Al2O3) have been grown by sequential pulsed laser deposition. The formation of well isolated quasispherical nanocrystals is observed for samples with Fe content per layer close to 6.5×1015 atoms/cm2. Increasing the Fe content leads first to the formation of elongated nanocrystals and then to quasicontinuous layers. The evolution in the shape and size of the nanocrystals is reflected in the magnetic behavior of these systems. A crossover from a low temperature ferromagnetic regime to a high temperature superparamagnetic regime is observed at a temperature of 23 K in the samples containing isolated quasi-spherical nanocrystals. In this case, a reduced moment per Fe atom (1.4 μB/atom) with respect to the value for α-Fe (2.2 μB/atom) is estimated. This behavior is attributed to the presence of a Fe-oxide surface shell on the nanocrystals. The large values of the estimated effective magnetic anisotropy (1.4×106 J/m3) and the low temperature coercivity in these samples are attributed to a strong surface contribution to anisotropy, whereas the temperature dependence of coercivity is attributed to thermal activation.

Original languageEnglish (US)
Pages (from-to)6268-6274
Number of pages7
JournalJournal of Applied Physics
Volume90
Issue number12
DOIs
StatePublished - Dec 15 2001

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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