Room temperature Scanning Hall Probe Microscopy in external Fields

Abstract

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.