Anisotropia magnética em filmes epitaxiais Fe/Mn, Fe/Mn/Fe e Fe/Mn/Co
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2013-06-07
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Universidade Federal de Goiás
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This work reports the study of magnetic anisotropy of Fe/Mn bilayers, and Fe/Mn/Fe and Fe/Mn/Co trilayers, grown by molecular beam epitaxy onto monocrystalline MgO(001) substrates. Samples were produced with the Fe layer grown at a temperature of 175 ° C, with a thickness of 5 or 10 nm, the Co layer grown at 50 ° C, with a thickness of 2 or 5 nm, and the Mn layer grown at temperatures of 50 ° C, 150 ° C or 175 ° C, with thicknesses in the range from 0.80 to 2.20 nm. The angular variations of the in-plane absorption field, at Q-band (33.9 Ghz) microwave frequency, reveal the presence of a large four-fold magnetic anisotropy in all studied films. In samples with thicker Mn layers, two uniform resonance modes of bcc-Fe and bcc-Co layers are excited by the microwave field. The angular variations of the in-plane absorption field reveal for both layers the presence of fourth order cubic magnetic anisotropy. Films with the Mn layer thickness exceeding 1.16 nm exhibits, however, only a single absorption mode due to the overlapping of Fe-bcc and Co-bcc uniform resonance modes. Experiments at X-band (9.4 GHz) microwave frequency reveal the excitation of non-aligned and non-resonant modes, suggesting, for samples with the Mn layer grown at low temperature, a non-collinear coupling between the magnetic layers in the presence of low-intensity magnetic fields. Four-fold magnetic anisotropy constants in the range from 3.0 x 105 to 4.8 x 105 erg/cm3 for the Fe layer, and from 2.0 x 105 to 6.4 x 105 erg/cm3, for the Co layer, are given by the experiments. The magnetic parameters deduced from the in-plane measurements at Q-band microwave frequency are used to fit the in-plane and out-of-plane angular variations of resonance fields at X-band frequency.
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PESSOA, Márcio Solino. Anisotropia magnética em filmes epitaxiais Fe/Mn, Fe/Mn/Fe e Fe/Mn/Co. 2013. 101 f. Tese (Doutorado em Física) - Universidade Federal de Goiás, Goiânia, 2013.