Magnetism of Nonmagnetic Layrs in Magnetic/Nonmagnetic Metallic Multilayrs

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1.Magnetic polarization of Au layrs in M/Au (m=Fe, Co, Ni) multilayrs with ^<119>Sn probes in the Au layrs was investigated from the Sn Mossbauer spectra. The magnitude of the polarization is Co/Au>Fe/Au>Ni/Au (Au thickness s_<Au><=20*)and Fe/Au>Co/Au>Ni/Au (d_<Au>>20*). The polarization penetration into the Au layr is different among three systems. In the Fe/Au, the polarization monotonically decreases from the interface to the inside of the Au layr. In the Co/Au, the attenuation of the polarization is slow below a certain Au thickness. Above this thickness, the polarization suddenly becomes small throughout the Au layr. In the Ni/Au, the polarization is small but almost constant through the Au layr. No proportional relation is observed between the temperature dependence of the magnetization and that of the Au polarization. Both parallel and antiparallel polarizations are confirmed to the magnetization direction, suggesting an oscillatory behavior of the polarization.2.To obtain complementary information to the Sn insertion case, Co/Au multilayrs with ^<57>Fe probes in the Au layr were investigated from the Fe Mossbauer spectra. The interpretation of the Fe spectra is not so easy as that of the Sn spectra because the Fe has magnetic moment. Nevertheless the results are qualitatively consistent to that of the Sn case if we assume that the polarization of the Au layr suppresses a superparamagnetic relaxation of the Fe moment.3.^<57>Fe probes were inserted in the Co layrs of the Co/Au multilayrs with high saturation field as typical in systems with antiferromagnetic interlayr coupling, and it is considered whether the interlayr coupling exists or not. The origin of the high saturation field is not due to the indirect coupling but due to the competition between the perpendicular anisotropy and the magnetostatic energy.