Browsing by Subject "Magnetic imaging"

Filter results by typing the first few letters
Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    Direct magnetic imaging of ferromagnetic domain structures by room temperature scanning hall probe microscopy using a bismuth micro-Hall probe
    (Japan Society of Applied Physics, 2001) Sandhu, A.; Masuda, H.; Oral, A.; Bending, S. J.
    A bismuth micro-Hall probe sensor with an integrated scanning tunnelling microscope tip was incorporated into a room temperature scanning Hall probe microscope system and successfully used for the direct magnetic imaging of microscopic domains of low coercivity perpendicular garnet thin films and demagnetized strontium ferrite permanent magnets. At a driving current of 800 μA, the Hall coefficient, magnetic field sensitivity and spatial resolution of the Bi probe were 3.3 × 10-4 Ω/G, 0.38 G/√Hz and ∼ 2.8 μm, respectively. The room temperature magnetic field sensitivity of the Bi probe was comparable to that of a semiconducting 1.2μm GaAs/AlGaAs heterostructure micro-Hall probe, which exhibited a value of 0.41 G/√Hz at a maximum driving current of 2μA.
  • Thumbnail Image
    ItemOpen Access
    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.
  • Thumbnail Image
    ItemOpen Access
    Room Temperature Scanning Micro-Hall Probe Microscope Imagingof Ferromagnetic Microstructures in the Presence of 2.5 Tesla Pulsed Magnetic FieldsGenerated by an Integrated Mini Coil
    (Institute of Physics Publishing, 2002) Sandhu, A.; Masuda, H.; Oral, A.
    A unique magnetic imaging system comprising of a room temperature scanning Hall probe microscope with an integratedmini-coil capable of generating pulsed magnetic fields up to 2.5 Tesla (width of 3 ms) was developed for the direct andnon-invasive magnetic imaging of ferromagnetic micro-domains in the presence of extremely large external pulsed mag-netic fields without adverse vibrational disturbance of the sample during measurements. The system was successfully usedfor magnetic imaging of the erasure process of bit patterns on the surface of 1.4 MB written floppy disks and the dynamicsof micro-domain structures of demagnetized strontium ferrite permanent magnets under large external pulsed magnetic fields.
  • Thumbnail Image
    ItemOpen Access
    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.