Low-current sensing with specular spin valve structures

While magnetoresistive spin valve (SV) layered structures have been widely used in both analogue and digital applications, more recent specular nano-oxide-layer spin valves (NOL-SV) have been used in read head and related digital applications. In the paper, the authors report on the design, fabrication and fundamental characterisation of NOL-SV-based magnetoresistive sensing elements for low-current monitoring purposes. The sensitivity of NOL-SV devices is improved in two ways. On the one hand, NOL-SV structures display higher magnetoresistance levels when compared with standard SVs. On the other hand, the current paths are patterned into the chip during the microelectronics fabrication process, therefore decreasing the gap space between the current paths and the sensing magnetoresistors. The authors describe in detail the fabrication process and characterise the first fabricated prototypes. Currents of the order of 1 mA have proved to be measured. Moreover, the temperature drift and the frequency response of the elements have been measured.