Controll and Quantitative Analysis of Spin Disorder at Magnetic fractal Interface

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It is well known that the interfacial roughness plays an important role in the giant magnetoresistance (GMR) effect of magnetic multilayers like Fe/Cr, Co/Cu and so on. The interfacial roughness, atomic disorder at the interfaces, is expected to be accompanied with the magnetic disorder. Such magnetic disorder may directly affect on the GMR effect because the spin-dependent scattering of conduction electrons at the interface is believed to be essential to the GMR effect. However, little attention has been paid to the magnetic disorder at the interface in studying the GMR effect. In addition, the meaning of the term, interfacial roughness, seems not to be well-defined. In this study we defined the interfacial rouness as that described by self-affine the Fractal interface and made an effort to establish the quantitative analysis of the magnetic interfacial roughness.A focusing polarizing neutron device which consists of Fe/Si supermirrors was installed at a polarized neutron reflectometer, PORE, at High Energy Accelerator Organization in order to increase the intensity of incident polarized neutrons. We have successfully increased the neutrons more than twice using the new device.The correlation between interfacial roughness and the GMR effect in epitaxial Fe/Cr(001) multilayers was investigated by neutron and X-ray reflectivity measurements. The specimens were annealed under various conditions in vacuum so as to have different interfacial roughnesses. The detailed profile of the off-specula reflection was quantitatively analyzed by the self-affine-Fractal interface model. The magnetic interfacial roughness were very sensitive to the annealing process, on the other hand, those for the atomic interfacial roughness were less sensitive. This suggests that the magnetic interfacial foughness in dominant over the atomic interfacial roughness for the spin-independent electron scattering at the interface which is a disadvantage to the GMR effect.