Surfactant-Assisted Growth of Giant Magnetoresistive Magnetic Multilayers

9731733 Chopra这是用直流磁控溅射方法制备的自旋阀结构的NiO-Co-Cu基巨磁阻磁多层膜的研究。其目的是利用表面活性剂在原子水平上控制基本的薄膜沉积步骤，以改变界面的性质和薄膜的形态。这种方法应该导致对这些层状系统中磁输运性质的结构敏感性的基本理解。在多层膜的某一给定层上沉积适当数量的表面活性剂应该会改变表面能和界面能之间的平衡。潜在的表面活性剂物种(银、砷、锡、锑和铅)是具有大原子体积的软金属，其性质有利于它们在覆盖层生长过程中“漂浮”到表面，并留下具有光滑界面的完好层，不容易混合。利用扫描隧道显微镜和原子力显微镜研究了不含表面活性剂的自旋阀在原位和非原位生长不同阶段表面活性剂辅助的表面形貌演化。用X射线光电子能谱对表面活性剂的表面偏析进行了监测。测量了外场作用下的磁特性、磁畴结构和壁跃迁。由磁性薄膜和非磁性薄膜组成的人工调制磁性多层膜是当前研究的热点。这些系统具有潜在的器件应用，如使用垂直各向异性多层膜的磁光存储材料和用于高密度存储的下一代读取头。***

9731733 Chopra This is a study of NiO-Co-Cu-based "giant" magnetoresistive magnetic multilayers in spin valve configuration, deposited by dc-magnetron sputtering. The goal is to employ surfactants to control elementary film deposition steps at the atomic level in order to modify the nature of interfaces and film morphology. This approach should result in basic understanding of the structure sensitivity of the magneto- transport properties in these layered systems. Deposition of a suitable number of layers of a surfactant on a given layer of a multilayer should alter the balance between surface and interface energies. The potential surfactant species (Ag, As, Sn, Sb, and Pb) are soft metals having large atomic volumes, properties that favor their "floating" out to the surface during over-layer growth and leaving behind intact layers with smooth interfaces less prone to intermixing. Surfactant assisted evolution of surface topography with respect to surfactant-free spin valves is studied at different stages of film growth in-situ and ex- situ (using scanning tunneling microscopy and atomic force microscopy). Surface segregation of surfactants is monitored by X-ray photoelectron spectroscopy. Magnetic properties, domain structures and wall transition in applied field are measured. %%% Artificially modulated magnetic multilayers comprised of magnetic and non-magnetic films are the subjects of intense research. These systems have potential device applications as magneto-optical storage materials using multilayers with perpendicular anisotropy and as next-generation read-heads for high-density storage. ***