Direct and Real-Time Observation of Sub-Micron Domain Dynamics in Magnetically Biased Strontium Ferrite Permanent Magnets by Room Temperature Scanning Micro-Hall Probe Microscopy
Abstract
A room temperature scanning micro-Hall probe microscope (RT-SHPM) was used for imaging stray magnetic field fluctuations at the surfaces of strontium ferrite permanent magnets (SFM) in the presence of external bias fields. The RT-SHPM enables the extremely fast, non-invasive, and quantitative measurement of localized surface magnetic fields on the sub-micron-scale. A 0.8 x 0.8 sq micrometers GaAs/AlGaAs micro-Hall probe (300 K Hall coefficient = 0.3 Ohm/G; field sensitivity = 0.04 G/square root of Hz) with an integrated STM tip for precise vertical positioning was used as a magnetic field sensor. External bias fields (H(sub ex)) of up to 2700 Oe were applied parallel to the easy and hard axes of thermally demagnetized SFMs. Sample areas of up to 50 x 50 micrometers were imaged at a height of 0.3 micrometers above the SFM surface for each H(sub ex), with scan speeds of approximately one frame/second (128 x 128 pixels) enabling quasi-real time imaging in synchronization with bias field changes. RT-SHPM images of surfaces normal to the easy axis of demagnetized samples at H(sub ex) = 0, clearly showed the presence of 8-15 micrometers sized domains and stray magnetic field fluctuations of +/- 200 G images of surfaces normal to the hard axis showed 20 micrometers sized domains with magnetic field fluctuations of +/- 100 G. Pronounced domain movement and rotation was observed for surfaces normal to the easy axis at bias fields above 700 Oe applied along the easy axis. A good correlation was found between domain movement and vibrating sample magnetometer hysteresis measurements. The RT-SHPM system was demonstrated to be a valuable tool for the direct and non-invasive study of micro-magnetic phenomena in ferromagnetic materials.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2001
- Accession Number
- ADP012291
Entities
People
- Adarsh Sandhu
- Ahmet Oral
- Hiroshi Masuda
- Naoji Iida
- Simon J Bending
Organizations
- University of Bath