Remote two-dimensional imaging of giant magnetoresistance with spatial resolution

Spatially resolved two-dimensional images of giant magnetoresistance (GMR) are demonstrated in Co/Cu and CoFe/Cu multilayers by remote imaging of the sample temperature using an infrared charge coupled device camera. We have previously shown that the emissivity of a giant magnetoresistive material at infrared wavelengths is related to its electrical resistance [S. M. Stirk et al., Appl. Phys. Lett. 86, 102505 (2005)]. Here, the change in emissivity in an applied magnetic field is sensed by the camera as a field dependent temperature image. Using the inherent spatial resolution of the camera, we characterize the GMR on a spatial scale of 200 microns across the sample surface. In a small sputtered Co/Cu multilayer sample, a significant variation of the GMR over the sample surface is observed, a characteristic previously undetectable by conventional electrical measurements. By contrast, no such spatial variation of the GMR is observed from a commercially grown CoFe/Cu wafer. These measurements demonstrate the potential for quick and remote imaging of magnetoresistance with spatial resolution with possible applications such as the whole wafer characterization of GMR materials and the magnetoresistance in patterned arrays.