The introduction of magnetic elements into electronic devices is beginning to be seen in both commercial products as well as purely research devices. The Transport phenomena, not only depend on electrons, but also depend on its spin is becoming important. Probably, the discovery of giant magnetoresistance(GMR) in 1988 is the most important turning point in this field. Baibich et al. observed huge change of resistance, 44 %, in antiferromagnetically coupled Fe/Cr magnetic mutilayered structure at 4.2 K. After that, in Co/Cu multilayered structure, magnetoresistance change of more than 100 % was found. It has been also studied when the magnetic metal elements are particles entrained in a nonmagnetic metal host (granular GMR ). Since that, discovery of the GMR effect in metal multilayers, in which the current was carried in the plane of the layers (CIP), GMR has also been observed when the current is carried perpendicular to the plane of the layers (CPP).
The physical origin of the GMR in terms of spin-dependent scattering of conduction electrons at the interfaces between the two magnetic layers and non-magnetic layer was also proposed by Baibich et al.. The spin-dependent scattering was more enhanced in CPP geometry than CIP geometry. We had an eye to synthesize the advantages of CPP and CIP geometry.
The key idea to make such a synthesized GMR structure was based on `periodic coercivity structure' in film plane. Periodic coercivity structure was intended by 3 different ways. The First attempt was made by using exchange coupling interaction between ferromagnetic material and antiferromagnetic material. The Second was two different ferromagnetic materials, and the third was coercivity difference resulted from thickness difference in magnetic multilayered system. To make this periodic coercivity structure in microscopic scale, we had adopted lithography technique which is very common in semiconductor industry.
While making the periodic coercivity structure on magnetic films, we had investigated the induced magnetic field effect on magnetic layer according to its direction especially, and had explored microscopic lithography technique using glass substrate which was not common in typical lithographic area.
Finally we have fabricated the periodic coercivity structure in film plane using lithography technique and 3 different ways as mentioned, and investigated its characteristic magnetoresistance. Consequently, we have observed abnormal magnetoresistance phenomena in periodic coercivity structure which is believed to be `spin-dependent scattering' effect.
