Superparamagnetic particle embedded microprobe (SPEM) for GMR sensor sensitivity calibration

The purpose of this work is to establish a standard sensitivity calibration protocol for GMR (Giant MagnetoResistive) spin valve sensors using superparamagnetic particle embedded microprobes (SPEM). Comparing to other calibration methods, such as the use of MFM (Magnetic Force Microscope), sealed fluidic flow cells, current lines, etc., the proposed SPEM method has four major advantages: no magnetic background, a precisely controlled number of particles which is mostly single-layered, pristine GMR surface after calibration, and mass fabrication. The SPEM is made from a superparamagnetic particle embedded SU-8 post and a glass cantilever. It can calibrate the magnitude of GMR signals to the number of superparamagnetic particles by bringing a known number of single-layered particles close to the GMR surface while still keeping the GMR surface pristine for future biofunction.