利用X射线磁性圆二色吸收谱计算3d过渡族磁性原子的轨道和自旋磁矩

在4个方面研究了实验数据的预处理和应用加和定则中的问题.1)外磁场对样品电流法测量的吸收谱强度的影响.发现外磁场H<200×10^-4T时，信号强度正比于H^-β；当H>200×10^-4T时，尽管外磁场继续增加，但信号强度基本保持不变.2)不同方向的电磁铁剩磁会导致吸收谱的分离.这种分离与入射光的偏振态和样品的磁性无关，可以通过乘以一个常数很好地消除这种分离.3)通过XPSPEAK 4.1对实验数据拟合，写出了吸收谱的解析函数.利用解析函数的积分值，建立一种相对“客观"的标准，判断在一定的实验条件下，不同的数值积分方法的准确性.4)以误差函数作为吸收谱的背景函数，建立了一套完整的X射线磁性圆二色的数据处理方法.最后用Bode积分法计算出20nm厚Co膜的轨道和自旋磁矩分别为0.141μ_B和1.314μ_B.关键词：X射线磁性圆二色加和定则台阶函数吸收谱拟合

Calculation of spin and orbital moments of 3d transition metals using X-ray magnetic circular dichroism in absorption

X-ray magnetic circular dichroism(XMCD) in absorption has been extensively used to determine spin and orbital moments by applying the sum rules to the absorption spectra of specified atoms. Due to quench of orbital moments in 3d transition metals, it is necessary to reduce errors in experiments and data analysis. In this article we focas on the data analysis in 4 aspects. 1) The influence of applied magnetic field H on signal intensity. Experiments reveal that, for H<200Gs the signal intensity measured in a way of drain current is proportional to H^-α; for H>200Gs, it changes little with the increase of H. 2) There is a separation between absorption spectra resulting from the iron-core remanence being in the parallel or antiparallel directions. This separation is independent of incident X-ray polarization and can be eliminated by multiplying by a constant. 3) An analytic form of absorption spectrum was obtained by fitting experimental data using XPSPEAK 4.1. It can be used as a criterion to determine which numerical integration method is suitable under certain experimental conditions. And, 4) by choosing an error function as a background to be subtracted from the X-ray absorption spectra, a method of calculation of spin and orbital moments from XMCD absorption spectrum is also developed Finally, the spin moment, of 1.314μ_B and orbital moment of 0.141μ_B of cobalt atom in a 20nm thick cobalt film are figured out based on Bode rule numerical integration.