Study of Metallic Multilayers Consisting of Magnetic and Superconducting Components

本研究的主题是研究人工结构的超晶格中的磁性和超导行为，并发现它们相互作用的新现象。为此，利用连接到超高真空沉积系统的氧化室，在原子尺度上控制厚度，制备了超薄金属层，从而制备了超薄氧化膜。为了测量磁化强度，采用了振动磁强计。磁性/非磁性多层材料的研究取得了显著进展，人工制备的铁磁性单层材料也得到了研究。近年来人们发现层间耦合是一个有趣的研究课题。在70 A左右，发现Fe层与Au层之间的相互作用改变了符号。在Fe/Cr和Cu/Co/Cu/Ni （Fe）等具有反平行磁性结构的多层材料中发现了一种新型磁电阻。前者通过层间反铁磁耦合实现了反平行结构，并通过中子衍射直接证实了反平行结构的存在。在后一种情况下，矫顽力场的差异是反平行自旋结构的原因，因此非常小的场就可以引起磁流变。如此大的磁阻效应被认为是人造金属多层材料的特征。垂直于多层膜方向的输运现象是一个非常有吸引力的问题。用于隧道测量的样品是用氧化室制备的。

The subject of this research is to study the magnetic and superconducting behaviors in artificially structured superlattices and to discover any new phenomenon as a result of their interplay. For this purpose, an experimental setup has been performed to prepare ultrathin oxide films by using the oxidation chamber connected to the ultrahigh vacuum deposition system, where ultrathin metal layers are prepared by controlling the thickness on an atomic scale. For the magnetization measurements, a sample-vibrating magnetometer was equipped.A remarkable advance was achieved in the study of magnetic/nonmagnetic multilayers and artificially prepared ferromagnetic monolayer systems have been investigated. It has been recently found that the interlayer coupling is an interesting subject. The interaction between Fe layers through Au layer was found to change the sign at about 70 A.A new type magnetoresistance was found in multilayers with antiparallel magnetic structure, such as Fe/Cr and Cu/Co/Cu/Ni (Fe). An antiparallel structure is realized by an interlayer antiferromagnetic coupling in the former case, and the antiparallel magnetic structure has been directly confirmed by neutron diffraction. In the latter case, the difference of coercive fields is the cause of antiparallel spin structure and therefore the MR change can be induced by very small fields. Such large MR effects are regarded to be characteristic of artificial metallic multilayers.Transport phenomena in the direction perpendicular to the multilayered films are very attractive problems. Samples for the tunneling measurements are prepared by using the oxidation chamber.