A portable instrument for non-contact giant magnetoresistance measurements utilizing the magnetorefractive effect and infrared fibres

A portable, low-cost instrument is presented capable of non-contact giant magnetoresistance (GMR) measurements through correlation with the magnetorefractive effect. Each component has been optimized for signal-to-noise ratio, portability and economy. The final design incorporates a pulsable thin-film infrared emitter which floods the surface of the sample providing reflected radiation focused by a lens into an infrared transmitting fibre. This shields the signal and transports it to a lithium tantalate pyroelectric detector. The measurements are performed at 5 Hz, allowing phase sensitive discrimination to reduce noise levels. The instrument is tested on a CoFe/Cu GMR multilayer and its response demonstrated to compare very favourably with larger more expensive instruments providing new opportunities for the remote sensing of GMR.