Surfactant-Assisted Growth of Giant Magnetoresistive Magnetic Multilayers

这是一项用直流磁控溅射沉积自旋阀结构的nio - co - cu基“巨型”磁阻磁性多层膜的研究。目的是利用表面活性剂在原子水平上控制基本的膜沉积步骤，以改变界面和膜形态的性质。这种方法将使我们对这些层状体系中磁输运性质的结构敏感性有基本的了解。在多层膜的某一层上沉积适当数量的表面活性剂层，应改变表面和界面能之间的平衡。潜在的表面活性剂（Ag、As、Sn、Sb和Pb）是具有大原子体积的软金属，它们的性质有利于在层间生长过程中“浮”到表面，并留下完整的层，界面光滑，不易混合。利用扫描隧道显微镜和原子力显微镜研究了无表面活性剂自旋阀在原位和非原位生长的不同阶段的表面形貌演化。用x射线光电子能谱法监测表面活性剂的表面偏析。测量了磁场中的磁性、畴结构和壁跃迁。由磁性膜和非磁性膜组成的人工调制磁性多层膜是目前研究的热点。这些系统具有潜在的器件应用，如使用垂直各向异性的多层磁光存储材料，以及用于高密度存储的下一代读头。＊＊＊

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. ***