Magnetoimpedância e dinâmica da magnetização em multicamadas de Ni81Fe19/Ag e Ni81Fe19/Cu

Abstract

In this work, the magnetoimpedance (MI) and magnetization dynamics in multilayered Ni81Fe19/Ag and Ni81Fe19/Cu samples are studied. The samples were produced by magnetron sputtering at the Laboratório de Magnetistmo e Materiais Magnéticos da UFSM with Py=Ni81Fe19 thickness of 100Å and 200Å, while the Ag layers were grown with 7Å, 14Å, 25Å, 50Å, 100Å and 200Å in the case of Py/Ag samples. For the Py/Cu samples, the Py layer was kept constant at 100Å, while the Cu layer was kept with 25Å. The 15, 30, 50, 70 and 100 number of bilayers was kept in all set of samples. The magnetoimpedance measurements were performed in the frequency range 100kHz 1.8GHz. MI ratios of 240% were observed in the [Py(100Å)/Ag(25Å)]x100 system, while 253% was obtained in the [Py(100Å)/Cu(25Å)]x100 system at 1.8GHz and 709MHz, respectively. In the case of the Py/Ag samples, a multiple peak structure (4 to 6 peaks) was observed whenever the Py/Ag thickness ratio was 4. These multiple peak structures are possibly associated to multiple ferromagnetic resonance frequencies in these particular samples. The experimental relations of dispersion were obtained for all samples that presented FMR in the studied frequency range. The results are discussed in terms of the induced magnetic anisotropies associated to the sputtering guns and also taking into account the more important interactions between the magnetic layers.