The Effect of Pb on the Interface Structure of Fe/Cr(100) Metallic Multilayers
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The Effect of Pb on the Interface Structure of Fe/Cr(100) Metallic Multilayers Kyu-Young Kim, Masao Kamiko, Sang-Mun Oh, Guang-Hong Lu and Ryoichi Yamamoto Institute of Industrial Science, University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106-8558, Japan ABSTRACT We investigated the differences in the interface structures and magnetotransport properties between surfactant-mediated multilayers and normal ones. From the observations of RHEED and High-Resolution X-ray diffraction patterns, we confirmed that the surfaces of Fe/Cr(100) multilayers with Pb are flatter and the interfaces are sharper than one without Pb, which means that Pb operates as an effective surfactant. The magnetoresistance(MR) ratio of the multilayers prepared with Pb was larger than that of the multilayers prepared without Pb. The change of resistance with magnetic field was larger for the multilayers with a surfactant. INTRODUCTION Numerous observations have been reported, indicating that interface roughness plays an important role in the giant magnetoresistance(GMR) effect. However, no clear picture has yet emerged and the reported data are contradictory. Petroff has reported that interfaces became rough by annealing in Fe/Cr multilayer prepared by MBE, and resulted in the increment of GMR [1]. However, Rencing has reported an opposite result that GMR of Fe/Cr multilayers with rough interfaces is smaller [2]. Therefore, it is important to get detailed information on the growth behavior and its effect on interface morphology. Surfactant epitaxy was introduced as a method of changing the growth mode from 3D-island growth to layer-by-layer growth [3]. The studies of surfactant epitaxy were applied for the homoepitaxy of metals [4,5], but there are few examples reported for the heteroepitaxy of metallic multilayers. There have been only few examples of application for the metallic multilayers [6,7]. Therefore, it is necessary to study whether the information from the growth experiment can be actually applied for preparing the metallic multilayer or not. EXPERIMANTAL DETAILS The Fe/Cr multilayers were grown by molecular beam epitaxy (MBE) equipped with RHEED. A MgO(100) single crystal was used as a substrate. The substrate was cleaned by heating at 850Û& for 10 min. Cr(or Fe) of 100Å was deposited at 200Û& as a buffer layer and was then annealed at 850Û& for 30 min to obtain a flat surface. We chose Pb as the surfactant atoms. To clarify the mechanism of surfactant epitaxy, the thickness was varied between 0.2Å and 2.4Å(1ML). The deposition rate of Pb was controlled at 0.01Å/s ~ 0.03Å/s. The growth temperature was varied from room temperature to 200Û&. The morphology of the surface after deposition was confirmed by Atomic Force Microscope. Fe/Cr multilayers were fabricated on a buffer layer, which was composed of 100Å Cr and 20Å Fe deposited at 200Û& and was then annealed at 850Û& for 30 min. The deposition P3.35.1
rates of Fe and Cr were 0.02~0.07Å/s. The deposition temperature was maintained at 200Û& during preparation of the Fe/Cr multilaye
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