Study on a symbiotic combination of the high-Tc superconducting magnetic shield and the ferromagnetic one with magnetic shaking

高温超导磁屏蔽与磁振荡铁磁屏蔽共生组合研究

基本信息

批准号：
03805035
负责人：
SASADA Ichiro
金额：
$ 1.73万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

The amplitude of the trapped flux in high-Tc superconductors is strongly affected by the frequency of the magnetic field applied during cooling and the cooling rate. The amplitude is small when the frequency is high or the cooling rate is low.For example,dc magnetic field was trapped in a BiSrCaCuO high-Tc superconducting bulk plate almost as it was;however,ac magnetic field of 10Hz was trapped 1/43 times as small as the amplitude applied to the sample.This nature of the trapped flux allows a new symbiotic combination of ferromagnetic shield with magnetic shaking and high-Tc superconducting magnetic shield.In this combination,the earth's field causing a trapped-flux problem can be attenuated to as small as 0.1mG by the ferromagnetic shield with magnetic shaking whereas any care to suppress the leakage of the shaking field is not needed,making the ferromagnetic shield very thin and lightweight.A miniaturized fluxgate magnetometer(resolution as high as 0.46mG at 77K)is useful to measure the distribution of the trapped flux in high-Tc superconductors,in which,by encapsulating the tip of the core with a piece of copper,the specimen can be avoided to be exposed to high-frequency exciting field of the order of 1G whereas it is transparent to the trapped flux.Amorphous magnetic material(Metglas 2705M)with highly rectangular B-H loop exhibits large enhancement of shielding performance by magnetic shaking which is 20-30 times better than Permally.

高温超导体中俘获磁通的振幅受到冷却过程中施加的磁场频率和冷却速率的强烈影响。当频率较高或冷却速率较低时，振幅较小。例如，BiSrCaCuO高温超导块体板中几乎原封不动地捕获了直流磁场；而10Hz的交流磁场则捕获了1/43与施加到样品上的振幅一样小。捕获磁通的这种性质允许铁磁屏蔽与磁振动和高温超导磁屏蔽的新共生组合。在这种组合中，地球场引起具有磁振动的铁磁屏蔽可以将俘获通量问题衰减至小至0.1mG，而无需任何抑制振动场泄漏的措施，使得铁磁屏蔽非常薄且轻。小型化磁通门磁力计（分辨率77K 时高达 0.46mG）可用于测量高温超导体中俘获通量的分布，其中通过用一块铜封装磁芯的尖端，可以避免样品暴露在1G量级的高频激励场中，同时它对俘获磁通是透明的。具有高度矩形B-H环的非晶磁性材料（Metglas 2705M）通过磁振动表现出极大的增强屏蔽性能，这是比 Permally 好 20-30 倍。