Control of Interface Structure for Oxides Artificial Lattices

作为制备氧化物人工超晶格的方法之一，采用金属靶的交替反应溅射法有望成为一种有效的方法。我们进行了铁氧化物薄膜的沉积和氧化的铁靶，通过使用Ar和氧气的基础研究。X射线吸收近边结构（XANES）测试表明，在4 mTorr氧分压下溅射的氧化铁薄膜中含有Fe_3O_4和γ-Fe_3O_4。在10 mTorr氧气氛下沉积的薄膜主要由α-Fe_3 O_4组成。我们发现薄膜中有很大的磁阻效应，同时也显示出很高的电阻率。这种磁阻效应可达4%，约为常规块状Fe_3O_4的10倍。透射电镜分析表明，薄膜为Fe_3O_4柱状结构，直径约为30- 40 nm。另一方面，作为真实的多层氧化物之一，我们设计了Bi取代的铁石榴石多层结构，用于磁光记录介质。利用层间晶格失配引起的逆磁致伸缩效应，将薄膜设计成具有垂直磁各向异性。

As one of the method for fabricating oxides artificial super lattices, alternative reactive sputtering method by using some metal targets is expected to be useful. We performed the basic investigation of deposition and oxidization of iron oxides thin films from an iron target by using Ar and Oxygen. From the XANES (X-ray absorption near edge structure) measurements, iron oxide thin films are containing Fe_3O_4 and gamma-Fe_3O_4 for the films sputtered under 4mTorr of oxygen partial pressure. The films sputteredunder 10mTorrof oxygen mainly consist of alpha-Fe_3O_4. We found a big magnetoresistive effect in the films which also show a high specific resistivity. This magnetoresistive effect is as large as 4% and it is about ten times big as the value for conventional bulk Fe_3O_4. From the structural analysis by using a transmission electron microscope, the films show a culumnar structure of Fe_3O_4 and its diameter is roughly 30-40nm.On the other hand, as one of the real multilayrs of oxides, we designed the multilayr structures of Bi-substituted iron garnet films for the purpose of megneto-optical recording media. The films are designed for having perpendicular magnetic anisotropy by utilizing the reverse magnetostrictive effect caused by the lattice mismatch between the layrs.