Nanoconstricted structure for current-confined path in current-perpendicular-to-

2019-09-11 08:12:39

layer electron metallic oxide NOL

责任者: Fukuzawa, H.;Yuasa, H.;Koi, K.;Iwasaki, H.;Tanaka, Y.;Takahashi, Y.K.;Hono, K. 单位: Corporate Research and Development Center, Toshiba Corporation, Kanagawa 212-8582, Japan 来源出处: Journal of Applied Physics,2005,97(10):10-509 摘要: We have successfully observed a nanoconstricted structure for current-confined-path (CCP) effect in current-perpendicular-to-plane-giant-magnetoresistance (CPP-GMR) spin valves. By inserting an AlCu nano-oxide layer (NOL) formed by ion-assisted oxidation (IAO) between a pinned layer and a free layer, the MR ratio was increased while maintaining a small area resistance product (RA). The cross-sectional high-resolution transmission electron microscopy image of the sample with RA= 380 mΩ μ m2, ΔRA=16 mΩ μ m2, and MR ratio=4.3% showed that an amorphous oxide layer is a main part of the NOL that blocks the electron conduction perpendicular to plane. Some parts of the NOL are punched through crystalline, metallic channels having a diameter of a few nanometers, which are thought to work as nanoconstricted electron conduction paths between the pinned layer and the free layer. Nano-energy-dispersive-x-ray-spectrum analysis also showed that Cu is enriched in the metallic channels, whereas Al is enriched in the amorphous oxide region, indicating that the metallic channel is made of Cu and the oxide is made of Al2 O3. The nanoconstricted structure with good segregation between the metallic channel and the oxide layer enables us to realize a large MR ratio in CCP-CPP spin valves. © 2005 American Institute of Physics. 关键词: Giant magnetoresistance;Oxidation;Transmission electron microscopy;Crystallization;Lithography;Microstructure;Electron tunneling;Energy dispersive spectroscopy;Thin films;Magnetron sputtering;Nanoconstricted structures;Nano-oxide layer (NOL);Ion-assisted oxidation (IAO);Electron conduction