Browsing by Subject "Scanning Hall probe microscopy"

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    50 nm Hall Sensors for Room Temperature Scanning Hall Probe Microscopy
    (Institute of Physics Publishing, 2004) Sandhu, A.; Kurosawa, K.; Dede, M.; Oral, A.
    Bismuth nano-Hall sensors with dimensions ∼50nm × 50 nm were fabricated using a combination of optical lithography and focused ion beam milling. The Hall coefficient, series resistance and optimum magnetic field sensitivity of the sensors were 4 × 10-4 Ω/G, 9.1kΩ and 0.8G/√Hz, respectively. A 50nm nano-Bi Hall sensor was installed into a room temperature scanning Hall probe microscope and successfully used for directly imaging ferromagnetic domains of low coercivity garnet thin films.
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    Nano and micro Hall-effect sensors for room-temperature scanning hall probe microscopy
    (Elsevier, 2004) Sandhu, A.; Okamoto, A.; Shibasaki, I.; Oral, Ahmet
    GaAs/AlGaAs two-dimensional electron gas (GaAs-2DEG) Hall probes are impractical for sub-micron room-temperature scanning Hall microscopy (RT-SHPM), due to surface depletion effects that limit the Hall driving current and magnetic sensitivity (Bmin). Nano and micro Hall-effect sensors were fabricated using Bi and InSb thin films and shown to be practical alternatives to GaAs-2DEG probes for high resolution RT-SHPM. The GaAs-2DEG and InSb probes were fabricated using photolithography and the Bi probes by optical and focused ion beam lithography. Surface depletion effects limited the minimum feature size of GaAs-2DEG probes to ∼1.5 μm2 with a maximum drive current Imax of ∼3 μA and Bmin∼0.2 G/Hz. The B min of 1.5 μm2 InSb Hall probes was 6×10 -3 G/Hz at Imax of 100 μA. Further, 200 nm×200 nm Bi probes yielded good RT-SHPM images of garnet films, with Imax and sensitivity of 40 μA and ∼0.80 G/Hz, respectively.
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    Room temperature Scanning Hall Probe Microscopy in external Fields
    (Magnetics Society of Japan, 2001) Sandhu, A.; Masuda, H.; Oral, A.; Bending, S. J.
    A new versatile room temperature scanning Hall probe microscope system (RT-SHPM) was developed and used for the magnetic imaging of longitudinal magnetic recording media, low coercivity perpendicularly anisotropic iron garnet epitaxial layers, and demagnetized strontium ferrite permanent magnets placed in externally applied magnetic fields. The RT-SHPM incorporates an ultra-high sensitive sub-micron GaAs Hall probe (active area of ∼ 0.8x0.8 μm2; room temperature Hall coefficient of 0.3Ω/G; field sensitivity of 0.04 G/√Hz) with an integrated scanning tunnelling microscope tip for vertically positioning the probe in very close proximity to sample surfaces. The Hall probe is not magnetized by magnetic fields hence enabling the real time (∼1 frame/sec) measurments in external magnetic fields. Results described include the observation of otherwise sharp magnetic transitions in written floppy disks to coalesce into small islands under external fields greater than 1300 Oe and the transformation of magnetic bubble lattices into striped-maze patterns in Bi-substituted iron garnet epilayers in cycled external fields.
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    Room temperature sub-micron magnetic imaging by scanning hall probe microscopy
    (Japan Society of Applied Physics, 2001) Sandhu, A.; Masuda, H.; Oral, A.; Bending, S. J.
    An ultra-high sensitive room temperature scanning Hall probe microscope (RT-SHPM) system incorporating a GaAs/A1GaAs micro-Hall probe was used for the direct magnetic imaging of localized magnetic field fluctuations in very close proximity to the surface of ferromagnetic materials. The active area, Hall coefficient and field sensitivity of the Hall probe were 0.8 μm×0.8 μm, 0.3 Ω/G and 0.04 G/√Hz, respectively. The use of a semiconducting Hall probe sensor enabled measurements in the presence of externally applied magnetic fields. Samples studied included magnetic recording media, demagnetized strontium ferrite permanent magnets, and low coercivity perpendicular garnet thin films. The RT-SHPM offers a simple means for quantitatively monitoring sub-micron magnetic domain structures at room temperature.
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    Room-temperature scanning Hall probe microscope (RT-SHPM) imaging of garnet films using new high-performance InSb sensors
    (IEEE, 2002) Oral, Ahmet; Kaval, Murat; Dede, Münir; Masuda, H.; Okamoto, A.; Shibasaki, I.; Sandhu, A.
    The room-temperature scanning Hall probe microscopy (RT-SHPM) imaging of garnet films using high-performance InSb sensors was discussed. The high-performance InSb micro-Hall sensors were fabricated by optical lithography. It was found that the room-temperature noise figure of the InSb sensors was 6-10 mG/√Hz, which was an order of magnitude better than GaAs-AlGaAs two-dimensional electron gas sensors.