In Situ Quantitative Measurement of Structural and Magnetic Properties of Nano-Structured Cobalt Films and Wires

本课题研究了分子束外延（MBE）法制备的Co/Cu/Co三层外延和Co OwiresO的结构和磁性能。Co和三层薄膜分别生长在平面和相邻（阶梯束状）硅（111）表面上。利用高分辨率、低能电子衍射和扫描电子显微镜对衍射光束进行角剖面测量，在原位定量地确定了描述这些Co纳米结构的界面粗糙度和混合参数。利用表面磁光克尔效应（SMOKE）、铁磁共振和Van der Pauw方法原位获得了矫顽力、磁各向异性、交换耦合、磁电阻和磁不均匀性。原子力显微镜和磁力显微镜提供了形貌和磁畴壁结构的重要信息。此外，还研究了这些纳米结构的温度依赖性和磁稳定性。界面粗糙度与磁阻和磁交换耦合之间的定量关系及其温度依赖性将允许优化三层材料，使其在非常低的磁场下具有最大和热稳定的磁阻。这种材料在超高密度硬盘驱动器的磁读头中有应用。＊＊＊

9701488 Wang This project examines the structure and magnetic properties of epitaxial Co/Cu/Co trilayers and Co OwiresO prepared by molecular beam epitaxy (MBE). The Co and trilayer films are grown on flat and vicinal (step bunched) silicon (111) surfaces, respectively. The parameters describing the interface roughness and mixing of these Co nanostructures are determined quantitatively in situ from the angular profile measurement of diffraction beams using high resolution, low energy electron diffraction complemented with scanning electron microscopy. The coercivity, magnetic anistropy, exchange coupling, magneto resistance, and magnetic inhomogeneity are obtained in situ from the surface magneto-optic Kerr effect (SMOKE), ferromagnetic resonance, and the Van der Pauw method. Atomic force microscopy and magnetic force microscopy provide important information on morphology and magnetic domain wall structures. In addition the temperature dependence and magnetic stability of these nanostructures are studied. %%% The quantitative relationship between interface roughness and magneto resistance and magnetic exchange coupling and their temperature dependence will permit an optimization of the trilayer that has the largest and thermally stable magneto resistance at very low magnetic fields. Such materials have applications in magnetic read heads for ultrahigh density hard disk drives. ***