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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    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.
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    Real-time imaging of vortex-antivortex annihilation in Bi 2Sr2CaCu2O8+δ single crystals by low temperature scanning hall probe microscopy
    (IOP Institute of Physics Publishing, 2006) Dede, M.; Oral, A.; Yamamoto, T.; Kadowaki, K.; Shtrikman, H.
    Vortices in superconductors play an important role in operating limits and applications of the superconductors. Scanning Hall probe microscopes have proven themselves to be quantitative and non-invasive tools for investigating magnetic samples down to 50 nm scale. Penetration of vortices in high quality single crystal Bi2Sr2CaCu2O8+δ superconductor has been studied in real-time with single vortex resolution at 77 K using a low temperature scanning Hall probe microscope (LT-SHPM). Vortices have been observed to be annihilated by the antivortices in small M-H loops.
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    Room Temperature Scanning Micro-Hall Probe Microscopy Under Extremely Large Pulsed Magnetic Fields
    (IEEE, 2003) Sandhu, A.; Masuda, H.; Oral, A.
    Abstract The versatility of a room-temperature scanning Hall probe microscope system with an integrated minicoil capable of generating pulsed magnetic fields up to 2.9 T was demonstrated by imaging magnetic structures on the surface of 1.4-MB floppy disks and demagnetized strontium ferrite permanent magnets. Vibration isolation between the sample and minicoil was achieved by using a combination of quartz glass plates and silicone gel layers and enabled extremely fast measurements under fields as high as 2.9 T, without detrimental effects on a GaAs-AlGaAs micro-Hall probe sensor located at a height of 0.5 mum above-the sample surface.
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    Scanning Hall probe microscopy (SHPM) using quartz crystal AFM feedback
    (American Scientific Publishers, 2007) Dede, Münir; Ürkmen, Koray; Girişen, Ö.; Atabak, Mehrdad; Oral, Ahmet; Farrer, I.; Ritchie, D.
    Scanning Hall Probe Microscopy (SHPM) is a quantitative and non-invasive technique for imaging localized surface magnetic field fluctuations such as ferromagnetic domains with high spatial and magnetic field resolution of ∼50 nm and 7 mG/Hz 1/2 at room temperature. In the SHPM technique, scanning tunneling microscope (STM) or atomic force microscope (AFM) feedback is used to keep the Hall sensor in close proximity of the sample surface. However, STM tracking SHPM requires conductive samples; therefore the insulating substrates have to be coated with a thin layer of gold. This constraint can be eliminated with the AFM feedback using sophisticated Hall probes that are integrated with AFM cantilevers. However it is very difficult to micro fabricate these sensors. In this work, we have eliminated the difficulty in the cantilever-Hall probe integration process, just by gluing a Hall Probe chip to a quartz crystal tuning fork force sensor. The Hall sensor chip is simply glued at the end of a 32.768 kHz or 100 kHz Quartz crystal, which is used as force sensor. An LT-SHPM system is used to scan the samples. The sensor assembly is dithered at the resonance frequency using a digital Phase Locked Loop circuit and frequency shifts are used for AFM tracking. SHPM electronics is modified to detect AFM topography and the frequency shift, along with the magnetic field image. Magnetic domains and topography of an Iron Garnet thin film crystal, NdFeB demagnetised magnet and hard disk samples are presented at room temperature. The performance is found to be comparable with the SHPM using STM feedback.