Microfabricated synthetic ferrimagnetic elements and their application to high density memory devices

利用聚焦离子束对人工合成的亚铁磁薄膜和交换偏置双层膜进行了微加工，并利用磁力显微镜对它们的磁畴结构进行了成像。此外，利用磁X射线显微镜成像技术进行了研究。(1)采用磁控溅射法制备了NiFe/Ru/NiFe合成亚铁磁薄膜，并对其磁性能进行了测试。通过优化溅射条件，得到了充分的反铁磁耦合。(2)采用直径约100 nm的Ga^+离子束聚焦技术制备了正方形、长方形和椭圆形磁性元件。正方形NiFe（12 nm）/Ru（0.3 nm）/NiFe（10 nm）单元中观察到闭合畴结构，而1：3矩形和椭圆形单元中观察到单畴结构。还研究了畴结构对薄膜结构的依赖性。(3)利用透射X射线显微镜对磁光记录介质上磁场调制法记录的磁畴结构进行了成像。小于100 nm长度的小标记被发现通过使用X射线显微镜清晰地成像。最小标记长度的依赖性的膜的组成进行了研究。基于Huth模型的模拟结果与实验结果相吻合。

Synthetic ferrimagnetic films and exchange biased bilayers were microfabricated by focused ion beam, and their magnetic domain structures were imaged by magnetic force microscopy. In addition, imaging technique using magnetic X-ray microscope was investigated.(1) NiFe/Ru/NiFe synthetic ferrimagnetic films were prepared by magnetron sputtering and their magnetic properties were measured. Sufficient antiferromagnetic coupling was confirmed to obtained by optimizing the sputtering condition.(2) Square, rectangular, and ellipsoid magnetic elements were fabricated by focused Ga^+ ion beam having 〜100 nm diameter. Closure domain structure was observed for the squared NiFe(12 nm)/Ru(0.3 nm)/NiFe(10 nm) elements, and single domain structure was obtained in the 1:3 rectangular and ellipsoid elements. The dependence of the domain structure on the film construction was also investigated.(3) Domain structure recorded by a magnetic field modulation method on the magneto-optical recording media was imaged by using transmission X-ray microscope. The small marks less than 100 nm lengths were found to be clearly imaged by using X-ray microscope. The dependence of the minimum mark length on the film composition was also investigated. The experimental results were found to be explained by the simulation based on Huth's model.