Fabrication of Bismuth Thin Films Nano-Hall Sensors for Room Temperature Scanning Micro-Hall Probe Microscope Imaging of Ferromagnetic Microstructures

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A fundamental understanding of the behavior of magnetic domains in external magnetic fields is important for the development of information technology such as ultra-high density magnetic recording media, high coercivity permanent magnets and multilayered ferromagnetic structures used for fabricating novel ‘spintronic'' devices. We have developed a room temperature scanning Hall probe microscopy (RT-SHPM) for the non-invasive and quantitative imaging of localized stray fields at the surfaces of ferromagnetic magnetic microstructures in the presence of pulsed external magnetic fields of 3 T Oe. However, advances in magnetic recording media have led to increasing demands for improvements in the spatial resolution of SHPM which using semiconducting GaAs/AlGaAs micro-Hall sensors is limited to 1.0 x 1.0μm due to surface depletion effects.The use of bismuth (Bi)(a semimetal, which exhibits a large Hall coefficient and negligible surface depletion) for fabrication of submicron Hall sensors sh … More ows promise as a means of improving the spatial resolution of RT-SHPM technology. Conventional MFM systems have a spatial resolution of 〜100nm, a figure which serves as a benchmark and target for studies on spatial resolution.In this research we succeeded in fabricating 50nm x 50nm Hall sensors using Bi thin films deposited by thermal evaporation. The electrical properties of the films were improved by post-deposition annealing in vacuum. The nano-Hall sensors were successfully used for magnetic imaging the surface of crystalline garnet thin films.This report describes the research carried out on "Fabrication of Bismuth Thin Films Nano-Hall Sensors for Room Temperature Scanning Micro-Hall Probe Microscope Imaging of Ferromagnetic Microstructures" as part of the Grant-in-Aid for Scientific Research (c)(2)for two years between 2003 and 2004. The fabrication and electrical characteristics of the Bi nano-Hall sensors are described. Also, the use of the Bi-nanosensors for imaging garnet thin films is demonstrated. Less