Magnetic behavior of Fe:Al₂O₃ nanocomposite films produced by pulsed laser deposition
| Autor: | Dempsey, N. M., Ranno, L., Givord, D., Gonzalo, J., Serna, Rosalía, Fei, G. T., Petford-Long, Amanda K., Doole, R. C., Hole, D.E. |
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| Rok vydání: | 2001 |
| Předmět: |
[PACS] Structure of nanoscale materials
[PACS] Magnetic phase boundaries (including classical and quantum magnetic transitions metamagnetism etc.) [PACS] Magnetic properties of monolayers and thin films [PACS] Magnetic anisotropy [PACS] Other ferromagnetic metals and alloys [PACS] Nanocrystalline materials [PACS] Magnetization curves hysteresis Barkhausen and related effects [PACS] Fine-particle systems nanocrystalline materials [PACS] Pulsed laser ablation deposition [PACS] Surface magnetism |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| Popis: | 7 pags. ; 7 figs. ; 1 tab. 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 μβ/atom) with respect to the value for α-Fe (2.2 μβ/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. This work has been partially supported by the European Union (BRITE Project No. 98-0616) and the Spanish CICYT~TIC Project No. 99-0866. One of the authors (N. M. D.) had a Marie Curie fellowship from the European Union. The authors acknowledge the support of the French and Spanish governments (HF1998-0055) and the British Council-Spanish government (HB1998-0182) Integrated Actions scheme for travel. |
| Databáze: | OpenAIRE |
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