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

采用核共振散射这一新兴的超细磁场探测实验方法，对纳米结构金属薄膜中的局部电子自旋极化或局部磁性进行了研究。将Fe或rrsSn的穆斯堡尔跃迁能对应的x射线单色化成几meV的宽度，作为核探针注入到含有Fe或rrsSn的样品中。探测核共振散射的x射线被记录为时间的函数，得到“时间谱”。通过对实验装置的优化，成功地获得了单原子“铁”层沉积在Cr层上的时间谱。结果表明，不同Cr层厚度的样品以及Cr层下是否有铁磁性ssFe层的样品的时间谱存在差异。结果表明，由于ssFe/Cr界面处的磁挫折效应，下覆的铁磁性ssFe层的存在改变了Cr层的磁性结构和铁探针处的超精细磁场。采用单原子或亚原子层交替沉积法制备了l2i型XiYZ型Heuslar合金膜和b2型XY型人造合金膜。对于CosMnSn - Heuslar合金薄膜，在时间光谱中观察到美丽的周期性节拍模式，这反映了样品具有高度有序的晶体结构。对于CoSn人造合金，在室温和低温下，超细场都很小。这样，核共振散射为我们提供了一些其他实验方法无法获得的关于局部磁性的独特信息，也将适用于研究非平衡态下的电子自旋极化。

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.