Si缓冲层的生长温度对SiGe组分、结构的影响

利用同步辐射X射线高分辨衍射、掠入射表面衍射、原子力显微镜、电子显微镜等手段研究了SiGe外延层的生长质量、组分与作为缓冲层Si的生长温度之间的关系. 研究表明, 在外延薄膜中Ge的含量为32±2%; 当Si缓冲层生长温度在400—500\textcelsius范围内, SiGe外延层质量高, 没有生长位错出现. X射线反射及原子力显微镜则显示对应最光滑的SiGe外延层表面的Si缓冲层的生长温度为450\textcelsius, 相应的表面粗糙度仅为大约15\AA.     

沉积于MgO基片上的La0.7Ca0.3MnO3薄膜的应变弛豫和磁电阻特性

利用90°离轴射频磁控溅射方法将La_0.7Ca_0.3MnO₃(LCMO)沉积于(001)取向的MgO单晶基片上,薄膜厚度变化范围为5nm到200nm. 通过掠入射X射线衍射技术测量了LCMO/MgO薄膜的面内晶格常数, 结合常规X射线衍射研究了LCMO薄膜的晶格应变及其弛豫情况, 用四探针法测量了薄膜的磁电阻特性.结果表明, LCMO/MgO薄膜均为(001)取向生长, 在厚度小于5nm时已经发生应变弛豫, 当薄膜厚度为100nm以上时, 薄膜的微应变接近于完全弛豫, 并表现出与块体材料类似的磁电阻特性, 具有较大的磁电阻和较高的磁电阻峰值温度.     

Microstructural stability of NiO-containing spin valves annealed at room temperatur

Microstructure of NiO-containing Co/Cu/Co spin valves （CCC-SV） annealed at room temperature for nearly four years has been studied by synchrotron radiation X-ray diffraction. With the annealing time expanding, the thickness of each sub-layer remains nearly unchanged while the interface roughness varies obviously compared with that of samples without annealing. The roughness at the interface of NiO/Co decreases with the annealing time increasing for both of the samples with NiO layer on the top （TSV） and under the bottom （BSV） of CCC-SV. On the other hand, the roughness at Co/Cu interface increases with the annealing time expanding for BSV while it decreases for TSV. These results indicate that the structure of TSV is more stable than that of BSV.     

Effects of Si surficial structure on transport properties of La_(2/3)Sr_(1/3)MnO_3 films

La_(2/3)Sr_(1/3)MnO_3 films are deposited on(001) silicon substrates,in which the silicon surfaces have artificially been treated into the scallops-like,pyramid-like,and smooth polishing structure,by pulsed laser deposition.The magnetoresistances of the films on etched substrates under low applied field are very sensitive to the applied field,and much larger(14.3% for acid-etched,and 42.9% for alkali-etched) than that on the polished Si at 5 K.Zero-field-cooled and field-cooled magnetization behaviors are measured and analyzed.Remarkable upturn behaviors in temperature-dependent resistivity for all samples are observed at low temperature,which follows the Efros-Shkloskii variable range hopping law and the Arrhenius law.We believe that the rough surface may be useful in device design.     

Magnetic Damping Properties of Single-Crystalline Co55Mn18Ga27 and Co50Mn18Ga32 Films

We investigate the structural,static magnetic and damping properties in two Mn-deficient magnetic Weyl semimetal Co-Mn-Ga(CMG) alloy films,i.e.,Co₅₅Mn₁₈Ga₂₇(CMG1) and Co₅₀Mn₁₈Ga₃₂(CMG2),which were epitaxially grown on MgO(001) substrates.CMG1 has a mixing phase of B₂ and L21,larger saturation magnetization(Ms ～760 emu/cm³),stronger in-plane magnetic anisotropy.CMG2 has an almost pure B₂ phase,small...