Microstructural imaging of Ferromagnetic material using Integrated Quantum Well Hall Effect Sensor Arrays.

The detailed microstructures of a material can affect its mechanical, electrical and optical properties. In ferromagnetic materials, domain walls and grain boundaries are largely responsible for defining the microstructures. A key method to analyse the microstructure of a ferromagnetic material is to measure the Magnetic Field Leakage (MFL) from its grain boundary/domain walls. The vast majority of materials require a micro scale magnetic field sensor to image the grains and domains. In this work, high sensitivity low noise Quantum Well Hall Effect (QWHE) sensor arrays have been designed and fabricated using InGaAs-AlGaAs or metamorphic InGaAs-InAlAs heterostructures. A range of sensor arrays with individual sensor size varying from 400 µm² down to 4 µm² were prepared, packaged and mounted onto a precision XYZ stepper platform for magnetic field mapping. Clear images of both micron scale defects and microstructure image are demonstrated and analysed.