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

doi:10.1063/1.1415054

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

Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

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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 μ_B/atom) with respect to the value for α-Fe (2.2 μ_B/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 language	English (US)
Pages (from-to)	6268-6274
Number of pages	7
Journal	Journal of Applied Physics
Volume	90
Issue number	12
DOIs	https://doi.org/10.1063/1.1415054
State	Published - Dec 15 2001

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General Physics and Astronomy

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title = "Magnetic behavior of Fe:Al2O3 nanocomposite films produced by pulsed laser deposition",

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.",

author = "Dempsey, {N. M.} and L. Ranno and D. Givord and J. Gonzalo and R. Serna and Fei, {G. T.} and Petford-Long, {A. K.} and Doole, {R. C.} and Hole, {D. E.}",

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T1 - Magnetic behavior of Fe:Al2O3 nanocomposite films produced by pulsed laser deposition

AU - Dempsey, N. M.

AU - Ranno, L.

AU - Givord, D.

AU - Gonzalo, J.

AU - Serna, R.

AU - Fei, G. T.

AU - Petford-Long, A. K.

AU - Doole, R. C.

AU - Hole, D. E.

PY - 2001/12/15

Y1 - 2001/12/15

N2 - 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.

AB - 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.

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

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