Investigation on Local Electron-Spin-Polarization in Nano-Structured Magnetic Thin Films in Equilibrium andNon-Equiibrium States

为了研究纳米结构金属薄膜的局域电子自旋极化或局域磁性，应用核共振散射这一新发展起来的能够探测超精细场的实验方法，研究了纳米金属薄膜的局域磁性。对应于“Fe或rrsSn的穆斯堡尔跃迁能的X射线束被单色化成几个MeV的宽度，注入到含有”Fe或rrsSn的样品中作为核探针。记录了探测核共振散射的X射线随时间变化的“时间谱”，并对实验装置进行了优化，成功地获得了沉积在铬层上的单原子“Fe”层的“时间谱”。结果表明，不同铬层厚度的样品的时间谱不同，在铬层下有无铁磁性ssFe层的样品也有不同的时间谱。结果表明，由于界面磁阻效应，衬底铁磁性ssFe层的存在改变了Cr层的磁结构，改变了“Fe探针”处的磁超精细场。还测量了交替沉积单原子或亚原子层成分元素制备的L2I型XYZ Heuslar型合金薄膜和B2型XY人造合金薄膜。对于CoMnSnHeuslar型合金薄膜，在时间谱上观察到美丽的周期性拍频图案，这反映了样品实现了高度有序的晶体结构。对于CoSN人工合金，无论是在室温还是在低温下，超精细场都很小，因此，核共振散射为我们提供了一些其他实验方法无法获得的局域磁性信息，也适用于非平衡态电子自旋极化的研究。

Nuclear resonant scattering, a newly developing experimental method which can detect magnetic hyperfine field, was applied in order to study local electron-spin-polarization or local magnetism in nano-structured metallic thin films. X-ray beams corresponding to the Mossbauer transition energy of "Fe or rrsSn were monochromatized into a width of several meV and injected to the samples containing "Fe or rrsSn as nuclear probes. The X-rays resonantly scattered by the probing nuclei were recorded as a function of time to obtain "time spectra".After some optimization of the experimental setup, time spectra in good S/N ratio were successfully obtained for a monatomic "Fe layer deposited on a Cr layer. It was found that the time spectra were different among samples with different Cr layer thickness and also between samples with and without a ferromagnetic ssFe layer under the Cr layer. The results suggest that the magnetic structure of the Cr layer and also the magnetic hyperfine field at the "Fe probes are changed by the existence of the underlaid ferromagnetic ssFe layer due to the magnetic frustration effect at the ssFe/Cr interface.Measurements were also done for L2i-type XiYZ Heuslar alloy films and B2-type XY artificial alloy films, which were prepared by alternate deposition of monatomic or sub-atomic layers of ingredient elements. For CosMnSn Heuslar alloy films, beautiful periodic beat patterns were observed in the time spectra, which reflects the realization of samples with highly-ordered crystallographic structures. For CoSn artificial alloys, the hyperfine field was found to be small at both room temperature and low temperatures.In this way, the nuclear resonant scattering offers us some unique information on local magnetism which cannot be obtained by other experimental methods, and would also be applicable to the studies on ltral electron-spin-polarization in non-equilibrium states.