Anisotropia magnética em tricamadas epitaxiais Fe/Mn/Fe
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2010-04-08
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Universidade Federal de Goiás
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The ferromagnetic resonance (FMR) technique at the microwave frequencies of X-band (9.79 GHz) and Q-band (34 Ghz) was used to study, at room temperature, the magnetic anisotropy of Fe/Mn/Fe trilayers. The samples studied were grown by molecular beam epitaxy onto MgO substrates at the temperatures of 50 ° C, 150 ° C and 175 ° C, at the pressure of 4 x 10-11 Torr. The thicknesses of the distinct layers were 5 or 10 nm for the bottom Fe layer grown onto the MgO substrate, varied from 0.8 to 1.35 nm, for the Mn spacer layer, and was kept constant and equal to 5 nm, for the top Fe layer. The FMR
spectra of the symmetrical trilayer at X and Q-band microwave frequencies show only the uniform resonance mode. Asymmetrical trilayers also show non resonant and/or non aligned modes at X-band frequency, but only the uniform mode at Q-band frequency. For some samples this result gives evidence of a non-collinear coupling between the Fe layers in the presence of low intensity magnetic fields. The out-of-plane angular dependence of the absorption fields show that the magnetization for all trilayers studied is in the plane of the sample. The magnetic anisotropy was deduced from the in-plane angular dependence of the uniform resonance mode at Q-band frequency, taking the free energy of the magnetic system as the result of contributions from Zeeman, demagnetizing, and in-plane cubic magnetocrystalline anisotropy energies. Fourfold in-plane anisotropy fields of 600 Oe and effective magnetizations above 16000 G were observed. The set of results obtained shows the high sensitivity and versatility of the FMR technique to study the magnetic properties of epitaxially grown monocrystalline nanometric structures.
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PESSOA. M. S. Anisotropia magnética em tricamadas epitaxiais Fe/Mn/Fe. 2010. 85 f. Dissertação (Mestrado em Fisica)–Universidade Federal de Goiás, Goiânia, 2010.