Magneto-optical Kerr Eect Study of Magnetic Anisotropy in Soft Ferromagnets (original) (raw)
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In ferromagnetic thin films, the effect of the magnetic anisotropy dispersion on the quasi-static susceptibility measured under a static magnetic field is shown. An approach is presented to estimate the anisotropy distribution both in angle and intensity from static and dynamical magnetic measurements. Because the transverse biased susceptibility is not fully described by the single anisotropy model, in particular for H ?? HK, either a full magnetic anisotropy dispersion P(??,HK) without exchange energy or a double anisotropy modeling coupled by the exchange energy are introduced to access the observed behavior. These two extreme magnetic configurations are discussed.
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Magneto-optical Kerr effect (MOKE) magnetometry is one of the most widely employed techniques for the characterization of ferromagnetic thin-film samples. Some information, such as coercive fields or anisotropy strengths can be obtained without any knowledge of the optical and magneto-optical (MO) properties of the material. On the other hand, a quantitative analysis, which requires a precise knowledge of the material's index of refraction n and the MO coupling constants K and G is often desirable, for instance for the comparison of samples, which are different with respect to ferromagnetic layer thicknesses, substrates, or capping layers. While the values of the parameters n and the linear MO coupling parameter K reported by different authors usually vary considerably, the relevant quadratic MO coupling parameters G of Fe are completely unknown. Here, we report on measurements of the thickness dependence (0-60nm) of the linear and quadratic MOKE in epitaxial bcc-Fe(001) wedge-t...
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The effects of the deposition of ultrathin 57 Fe layers on both sides of the NiFe layers in NiFe/Cu multilayers were investigated by focusing on their structural, magnetic and magnetoresistance properties. Conversion electron Mössbauer spectroscopy measurements showed an out-of-plane magnetic anisotropy of the Fe layers. The magnetoresistance curves showed an unusual shape, where up to three peaks were observed. Eight variables computer simulations, based on a phenomenological model that considers bilinear and biquadratic couplings between layers with cubic and in-plane uniaxial anisotropies, were used in order to calculate the best-fitting magnetization curves for the NiFe/Cu and Fe/NiFe/Fe/Cu multilayers. Both model and Mössbauer spectroscopy results showed that it is the rotation of the Fe magnetic moment from out-of-plane to inplane orientation that provokes the unusual magnetoresistance curve shape. The observed reduction of the magnetoresistance amplitude with the addition of one monolayer of Fe in the NiFe/Cu multilayer was attributed to a less-effective spin-dependent scattering that occurs at Fe/Cu and Fe/ NiFe interfaces than at the NiFe/Cu interfaces.
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The effects of nanostructuration on the magneto-optic properties of ultrathin monocrystalline iron films grown on MgO ͑001͒ are investigated through the magneto-optic coefficients, which have a linear and quadratic dependence on the magnetization. The photon energy dependence of such magneto-optic coefficients is determined by measuring the relative variations of the reflectivity (⌬R pp /R pp) for p-polarized incident and reflected light ͑p-p polarized͒ when the magnetization rotates in the plane of the sample. Thick Fe films present a magneto-optical anisotropy, which has a quadratic dependence on the magnetization. Such anisotropy is strongly reduced in nanostructured iron thin films formed by nanometric iron islands. The modifications induced by the nanostructuration are stronger for the magneto-optical coefficients, which have a quadratic dependence on the magnetization in contrast to the linear terms. A self-consistent effective-medium formalism is presented that explains the modifications induced in the magneto-optical coefficients by nanostructuration.
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