The Effects of third Element for Hexagonal Ferrite Thin Films for High Density Magnetic Recording Medium with small grains

对于超高密度垂直磁记录，介质应具有化学稳定性、机械耐久性、中等硬磁性能和小颗粒。本文研究了溅射六方铁氧体薄膜中第三元素和底层对薄膜的晶体结构、磁性能和形貌结构的影响。结果表明，添加铋能有效地细化铁素体的晶粒度，矫顽力约为3.7kOe。该薄膜的线性记录密度为210~230kfrpi。在垂直记录介质中，制备具有垂直磁易轴取向的薄膜是非常重要的，在六方铁氧体中磁易轴是c轴。为了促进c轴取向，采用了具有c轴垂直取向的六方AlN作为底层。获得了约40 mA的增益尺寸和高达4.3 kOe的矫顽力，同时发现N元素向六方铁氧体中扩散。新的非晶态氧化铝底层被用来减小颗粒尺寸和磁性颗粒隔离。结果表明，非晶态铝薄膜可使晶粒度降至20im，薄膜的矫直力约为4kOe。该薄膜的磁耦合为静磁耦合，磁团簇大小约为40 nm。

For an ultra high density perpendicular magnetic recording, the media should have chemical stability, mechanical durability, moderate hard magnetic properties, and small grains. In this study, the effects of third element and under-layer for sputtered hexagonal ferrite thin films on crystallographic characteristics, magnetic properties, and morphological structure were studied. It was found that Bi addition was effective to reduce the grain size and coercivity was about 3.7 kOe. The linear recording density for this film was 210 to 230 kfrpi. In perpendicular recording media, it is very important to prepare the film with perpendicular orientation of magnetic easy axis, which is c-axis in hexagonal ferrite. To promote c-axis orientation, hexagonal A1N with c-axis perpendicular orientation was used as an under-layer. The gain size was reduced to about 40 ma and coercivity as high as 4.3 kOe was obtained, while diffusion of N into hexagonal ferrite layer was found. New under-layer of amorphous aluminum oxide was used for the reduction of grain size and for the magnetically grain isolation. It was found that amorphous aluminum uader-layer could reduce the grain to 20 im and coercivity of this film was about 4 kOe. Magnetic coupling of this film was magneto-static and magnetic cluster size, which was evaluated from MFM observation, was about 40 nm.