Preparation of nano-structured perpendicular magnetic recording media using porous alumina

通过对高纯铝板进行阳极氧化，形成多孔氧化铝或铝土层。在硫酸溶液中的阳极氧化形成了直径为15 nm、中心间距为40 nm的微孔。首先，我们用脉冲电镀的方法在孔中沉积了钴-铂合金。钴含量随着脉冲电压的增加而增加。垂直磁化曲线的垂直度在0.6~0.7之间。我们发现，通过施加铂种子，正方形大大增加到超过0.9的值。铂晶种的应用也导致了矫直力的增加。研究发现，铂晶种影响了HCP钴铂合金的晶体取向，增强了垂直各向异性。其次，比较了铂晶种和铜晶种沉积钴对磁性能的影响。铂晶种的矫顽力从没有晶种时的1.6kOe提高到2.5kOe，而铜晶种使其提高到2.0kOe。使用铂或铜种均可获得高达0.95的正方形。原因尚不清楚，为什么铂种子比铜种子更能增强矫顽力。最后，我们在气孔中沉积了铁-铂合金，以探索形成有序等原子铁-铂合金的可行性。沉积到气孔中的合金成分取决于镀液成分和脉冲电压。脉冲电压越高，铁含量越高。随着铁含量的增加，样品的矫顽力和正方度都变得更高。在真空中对近等原子组成的薄膜进行了热处理。尽管退火提高了矫直力，但仍未证实形成有序的铁-铂合金。为了制备含有等原子铁-铂合金的铝土膜，似乎需要更准确的合金成分分析。

Porous aluminum oxide layers or alumite layers were formed by anodic oxidizing high-purity aluminum sheets. The anodic oxidization in sulfuric acid solution resulted in the formation of micro pores 15 nm in diameter and 40 nm in center-to-center separation. First, we deposited cobalt-platinum alloy into the pores by pulse electroplating. The cobalt content increased with increasing pulse voltage. The squareness of perpendicular magnetization curve ranged from 0.6 to 0.7. We found that the squareness drastically increases to values exceeding 0.9 by applying platinum seed. The application of platinum seed also resulted in an increase in coercivity. The platinum seed was found to influence the crystallographic orientation of hcp cobalt-platinum alloy, enhancing the perpendicular anisotropy. Next, the effect of platinum seed on magnetic properties was compared with that of copper seed by depositing cobalt on them. The platinum seed enhanced the coercivity from 1.6 kOe without any seed to 2.5 kOe, while the copper seed increased it to 2.0 kOe. The squareness as high as 0.95 was attained using either of platinum or copper seed. The reason is not clear why the coercivity is more enhanced by the platinum seed than copper seed. Finally, we deposited iron-platinum alloy into the pores in order to investigate the feasibility of forming ordered equi-atomic iron-platinum alloy. The alloy composition deposited into the pores depended on bath composition and pulse voltage. Higher pulse voltages result in higher iron contents. The coercivity as well as squareness became higher with an increase in iron content. The films with nearly equi-atomic compositions were annealed in vacuum. Although the coercivity was enhanced by annealing, the formation of ordered iron-platinum alloy was not confirmed. More accurate analysis of alloy composition seems required to prepare alumite films containing equi-atomic iron-platinum alloy.