超导磁体剩余磁场对软磁材料测试的影响

Effect of superconducting magnet remanence on the soft magnetic material measurements

超导磁体体积小,能够获得强磁场,磁场稳定度、均匀度很高,因此,在磁学测量设备中应用很广泛.美国Quantum Design公司的高精度磁学测量系统采用的就是超导磁体,最高磁场能够达到7 T.由于超导磁体材料本身缺陷的钉扎作用,在磁体退磁后,磁体内部有剩余磁场,有时能够大于30 Oe.由此产生的磁场误差将导致测试的矫顽力、剩磁等数据不准确,甚至导致反向的磁滞回线.设置的磁场初始值不同,剩余磁场的大小也不同;初始磁场越大,剩余磁场越大.这种剩余磁场效应在软磁材料测试过程中表现得尤为明显,产生的测试误差不可忽略,必须进行磁场误差修正才能得到正确的结果.本文阐明了超导磁体产生剩余磁场的原因、影响因素和规律,详述了测试软磁材料可能遇到的问题,并给出解决方法.

The superconducting magnet is used to provide magnetic field in a magnetic property measurement system （SQUID-VSM, Quantum Design）, since it can provide high magnetic field up to 7 T. Due to the pinned magnetic flux, there is residual magnetic field as the magnetic field is set to be 0 from high field. There appears an error between the reported filed and the real filed. Sometimes, the residual magnetic field can be more than 30 Oe. It is so large that it may provide incorrect experiment data, such as Hc, Mr and inverted hysteresis loops. The effect of residual magnetic field on the soft magnetic material measurements should not be neglected. The residual magnetic field is dependent on initial magnetic field. The experimental data must be corrected by measuring the standard sample. In the paper we investigate the origin and the regular pattern of the residual magnetic field. The effects on the measurement results and the correction method are presented.