Magnetic properties of micro-structured exchange coupled bilayers

本研究的目的是制造3尺寸微结构化交换偶联Billayers，并为交换偶联领域的形成确定一种负责任的机制，使之与反磁域和墙的形成关系。在过渡金属合金和氧化物中， Cr-Al或NiO被选择为反磁网和Fe D220、D2 Ni、D280、D2 Permalloy被选择为铁磁网。在使用X射线差测仪、原子力显微镜和电子显微镜、亚微型交换偶联Billers对晶粒尺寸和晶体学方向之间的结构分析之后，对铁磁和抗磁层进行了结构分析，这些分析由电子豆光刻的平均值制造。磁域结构可以作为磁传输特性，然后用磁力显微镜和四个终端方法小心地测试了磁域结构。由于第一次，在亚微区域中出现了磁性反向过程，通过分析不同的磁性和平面霍尔效应。结果是用微观模拟计算的解磁性曲线进行比较的。它发现了一个可能的交换耦合场变体，以反映耦合区域的反向。进一步的变化斜率被发现以反映接口的粗糙度的程度，该接口确定了网络交换耦合到随机交换字段的强度。从这个实验研究中，交换耦合字段被显示为控制调整在亚微尺度上的耦合区域，并确定了反磁域大小。

The purpose of this study is to fabricate 3 dimensionally micro-structured exchange coupled bilayers, and to clarify a responsible mechanism for the exchange coupling field in relation to formation of the antiferromagnetic domains and walls. Amongst transition metal alloys and oxides, Cr-Al or NiO was chosen as an antiferromagnet and FeィイD220ィエD2NiィイD280ィエD2 permalloy was chosen as a ferromagnet. After the structural analyses on the grain size and crystallographic orientations between the ferromagnetic and antiferromagnetic layers with using X-ray diffractometer, atomic force microscope and electron microscope, submicron sized exchange coupled bilayers were fabricated by means of electron-bean lithography. The magnetic domain structure as well as magneto-transport properties were then carefully examined with magnetic force microscope and 4 terminal methods. For the first time, the magnetization reversal processes occurring in the sub-micron region was obtained by analyzing the anisotropy magnetoresistance and the planar Hall effects. The results were compared with the demagnetization curves calculated by micromagnetic simulation. It was found that the exchange coupling field varies proportional to the inverse of the coupling area. Furthermore the slope of the variation was found to reflect the degree of roughness at the interface which determines the strength of the net exchange coupling due to the random exchange field.From this experimental study, the exchange coupling field was shown to be controlled by adjusting the coupling area in submicron scale, which determines the antiferromagnetic domain size.