| Magnetic fields can occur over an extremely broad range of amplitudes, and spatial and temporal scales. Practical scientific and engineering systems have fields ranging in strength from pico-tesla to hundreds of tesla. Furthermore, spatial variations can range in scale from nanometers to tens of meters, and temporal variations can range from picoseconds to hours. Due to these large variations, many different devices and methods have been previously designed for measuring and mapping magnetic fields.;The primary application area for the systems developed here is magnetic microsystems. Such systems make use of one or more microscale electromagnets, soft magnets, and/or permanent magnets for sensors, actuators, inductors, electronics, biomedical devices, etc. A single magnet dimension may range from one mum to hundreds of mum, and the overall area of interest may span over distances of millimeters to centimeters. To map the stray fields from such structures, a field measurement tool must be capable of measuring fields ranging from mT to T, while mapping over distances of millimeters with a spatial resolution of approximately one mum. This current study is focused only on static fields, but time-varying fields are of great interest and could be addressed in further research.;This research focuses on the development of two tools that meet the requirements of microscale magnetic measurements. The first tool is based on an optical method and excels at extremely rapid measurements of large spatial regions. The second tool is a raster based system that focuses on high magnetic and spatial accuracy.;The optical system quantitatively maps the stray magnetic fields of microscale magnetic structures with field resolution down to 50 muT and spatial resolution down to 4 mum. The system uses a magneto-optical indicator film (MOIF) in conjunction with an upright reflective polarizing light microscope to generate optical images of the magnetic field perpendicular to the image plane. A novel single-light-path construction and discrete multi-image polarimetry processing method are used to extract quantitative areal field measurements from the optical images. The integrated system, including the equipment, image analysis software, and experimental methods are described. MOIFs with three different magnetic field ranges are calibrated, and the entire system is validated by measurement of the field patterns from two calibration samples. The final specifications for the MOIF system are: a spacial resolution of 4.2, 6.2, 20.1 mum for each respective MOIF type, a magnetic range of +/-230 mT with the use of the largest saturation MOIF film, magnetic resolution of +/-0.05, +/-0.5, +/-1 mT for each respective MOIF type, and quantification of a 2660 x 2128 mum area within tens of seconds.;The raster system, or scanning Hall probe microscope (SHPM), also quantitatively maps the stray magnetic fields of microscale magnetic structures, with field range of +/-1 T and spatial resolution down to 1.6+/-0.1 mum. The system uses a micro Hall sensor to accurately measure the magnetic field perpendicular to the sample surface. The micro Hall sensor is integrated onto the edge of a quartz tuning fork to accurately detect sensor-to-sample contact, allowing precise control of the measurement height. The sample is raster scanned beneath the sensor with a 3-axis stage system for measurement of a spatial magnetic map. The SHPM components completed during the design and construction are: a raster scan system and enclosure, a Novel AC spinning Gaussmeter, a micro Hall probe integrated on a distance-sensing quartz tuning fork, and a self-oscillating excitation circuit for height control. The final specifications for the SHPM system are: raster scan spatial resolution of 0.3 mum, an average sampling speed of one sample per 0.7 seconds, magnetic active area spacial resolution for the smallest active area Hall sensor (nominally one mum) of 1.6+/-0.1 mum, magnetic sensitivity of the 5, 10 mum Hall probes were 0.47+/-0.006, and 0.420+/-009 VT-1A-1 , respectively, although the current revisions of Hall sensors resistances are too high preventing their integration in the system. |
