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Study on Bi-Substituted Garnet Films with Strong Magneto-Optical Activity and High Corrosion Resistance for Magneto-Optical Disc.

磁光盘用强磁光活性和高耐腐蚀性双取代石榴石薄膜的研究。

基本信息

批准号：
61550223
负责人：
ABE Masanori
金额：
$ 1.41万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

项目摘要

Highly Bi-substituted garnet film is a promising medium for magnetooptical (M-O) memory because of its strong M-O activity and high corrosion resistance. We have investigated optimum conditions to get the Bi-substituted garnet film with (1) a large amount of Bi and (2) good homogeneity in quality. In particular, (2) is an important factor on applying a polycrystalline film to M-O medium; inhomogeneity causes so-called media noise, responsible for light scatter at grain boundary and irregular shape in thermomagnetically written bit.The films were prepared on glass substrates by rf-diode sputtering, which were crystallized by post-deposition annealing or in situ during sputterdeposition. For (1), we have successfully got the films cotaining a large amount of Bi up to 2.9 at a relatively low temperature of 520゜C, For (2) we have proposed measures to reduce media noise. It is composed of two procedures; one is to make the grain boundary optically undiscernible, the other to prevent the written bit domain from diffusing in shape. We could attain the former by sputtering in pure Ar or Ar+H_2 gases, instead of Ar+O_2gas. The sputtering in reducing atmosphere distributes crystal imperfections, such as defects and dislocations, in the grains homogeneously. We could improve the latter by adding a small amount of W (<1.2 at.%) which increases domain wall coercivity inside the grains.We have further investigated the origin of magnetic anisotropy of Co-substituted garnet film suitable to M-O media. The films were epitaxially in situ grown by rf sputtering. The substitution of Co was found to markedly enhance the stress-induced magnetic anisotropy because of large magnetostriction due to octahedrally coordinated Co^<2+>.

高Bi取代石榴石薄膜具有很强的磁光活性和抗腐蚀性，是一种很有前途的磁光存储介质。我们研究了获得Bi取代石榴石薄膜的最佳条件，该薄膜具有（1）大量的Bi和（2）质量均匀性好。（2）是影响多晶薄膜在M-O介质中应用的一个重要因素，非均匀性会引起所谓的介质噪声，导致晶界处的光散射和热磁写入位的不规则形状。对于（1），我们在520 ℃的较低温度下成功地得到了含Bi量高达2.9的薄膜。对于（2），我们提出了降低介质噪声的措施。它由两个过程组成：一是使晶界光学上不可辨别，另一个是防止写入的位域扩散的形状。前者可用纯Ar或Ar+H_2气体溅射，而不用Ar+ O_2气体溅射。在还原气氛中的溅射使晶体缺陷，如缺陷和位错，均匀地分布在晶粒中。通过添加少量的W（<1.2at.%）可以改善后者进一步研究了适用于M-O介质的Co取代石榴石薄膜磁各向异性的起源。薄膜是用射频溅射法原位外延生长的。由于八面体配位的Co^<2+>具有较大的磁致伸缩，Co的取代显著增强了应力诱导的磁各向异性。