  We report on a method by which we can systematically extract spectroscopic
information such as isotropic electron-nuclear hyperfine coupling constants
from near-zero field magnetoresistance spectra. The method utilizes a least
squares fitting of models developed from the stochastic quantum Liouville
equation. We applied our fitting algorithm to two distinct material systems:
Si/SiO2 MOSFETs, and a-Si:H MIS capacitors. Our fitted results and hyperfine
parameters are in reasonable agreement with existing knowledge of the defects
present in the systems. Our work indicates that the NZFMR response and fitting
of the NZFMR spectrum via models developed from the stochastic quantum
Liouville equation could be a relatively simple yet powerful addition to the
family of spin-based techniques used to explore the chemical and structural
nature of point defects in semiconductor devices and insulators.
