Preparation and Caracterization of Electrodeposited Magnetic Multilayrs

自从金属多层膜中垂直磁各向异性、磁光克尔效应和巨磁电阻效应的发现，极大地激发了人们对磁性多层膜纳米结构的研究兴趣。大多数磁性纳米结构薄膜已经通过溅射或分子束外延来制造，这已被证明是最适合于在原子尺度上控制制备高质量结构的方法。在这项工作中，我们发现，电沉积将被证明是一个很有前途的候选人制备磁性纳米结构，这取决于沉积过电位，因此生长机制。横截面透射电子显微镜，X-射线衍射，能量色散X-射线分析，俄歇电子能谱提供了证据的Co/Pt和Co/Cu纳米多层结构的电沉积电位控制下制备的连续层的组成调制。在Cu（111）衬底上生长的多层Co/Pt纳米结构具有较强的垂直磁化强度和较大的介电常数。在（111）面心立方织构的Co/Cu多层纳米结构中观察到了巨磁电阻效应和振荡反铁磁层间耦合。此外，一个大的饱和磁电阻超过20%的异质Co-Cu合金，其中包括在一个Cu-Cu基体中的Co-fcc富钴团簇在室温下已经实现。该值与先前在气相沉积超晶格以及异质合金中报道的值相当。进一步研究结晶动力学的成核和生长下精确的过电位控制是必要的，以实现改善的结构和磁性质量的电沉积纳米结构。

Since the discovery of not only perpendicular magnetic anisotropy and magneto-optical Kerr effect but also giant magnetoresistance in metallic multilayrs, interest in magnetic multilayred nanostructures has been greatly stimulated. Most magnetic nanostructured films have been fabricated by sputtering or molecular beam epitaxy, which have proved to be the most suitable for the controlled preparation of high-quality structures on an atomic scale. In this work we reveal that electrodeposition will prove to be a promising candidate for the preparation of magnetic nanosructures, which depend on the deposition overpotential and hence the growth mechanism. Cross-sectional transmission electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, and Auger electron spectoscopy have provided evidence for composition modulation across successive layrs in Co/Pt and Co/Cu nanometer-multilayred structures prepared by electrodeposition under potential control. Multilayred Co/Pt nanostructures grown on a Cu (111) substrate exhibit a remanent perpendicular magnetization and a large coercivity. Giant magnetoresistance and oscillatory antiferromagnetic interlayr coupling have been observed in a (111) fcc textured Co/Cu multilayred nanostructure. Moreover, a large saturation magnetoresistance of more than 20% has been achieved at room temperature for a heterogeneous Co-Cu alloy, which consists of ultrathin fcc Co-rich clusters in a nonmagnetic Cu matrix. This value is comparable to those previously reported in vapor-deposited superlattices as well as heterogeneous alloys. Further studies on the crystallization kinetics of nucleation and growth under precise overpotential control are necessary to achieve improved structural and magnetic qualities in the electrodeposited nanostructures.