Preparation and Caracterization of Electrodeposited Magnetic Multilayrs

自从在金属多层膜中发现垂直磁各向异性和磁光克尔效应以及巨磁电阻效应以来，人们对磁性多层纳米结构的兴趣大大增加。大多数磁性纳米结构薄膜都是通过溅射或分子束外延制备的，这被证明是最适合在原子尺度上控制制备高质量结构的方法。在这项工作中，我们揭示了电沉积将被证明是制备磁性纳米结构的一种很有前途的候选方法，这取决于沉积过电位，从而取决于生长机制。透射电子显微镜、X射线衍射仪、能谱分析和俄歇电子能谱为电位控制电沉积法制备的Co/Pt和Co/Cu纳米多层结构的连续层成分调制提供了证据。在Cu(111)衬底上生长的多层Co/Pt纳米结构显示出剩余的垂直磁化强度和较大的矫直力。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和反铁磁层间振荡耦合。此外，在室温下，由非磁性铜基质中的超薄面心立方富钴团簇组成的非均质Co-Cu合金获得了超过20%的大饱和磁阻。这一值与以前在气相沉积超晶格以及非均相合金中报道的值相当。为了改善电沉积纳米结构的结构和磁性，有必要在精确的过电位控制下进一步研究成核和生长的结晶动力学。

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.