Design And Preparation Of The Displacement Sensor Based On The Spin-valve Giant Magnetoresistance Materials

Compared with other types of sensor, giant magnetic resistance （GMR） sensorwas characterized by high sensitivity, small power consumption, low cost advantages,and especially can effectively detect weak magnetic field and change. The GMRsensor will bring a brand-new change in the field of industrial equipment automaticcontrol, trademark detection, and precision measurement technology.Ordered FeMn alloy nanowires were electrodeposited into the pores of AAOmembranes using single-bath. On the basis of that, NiFe/Cu/NiFe/FeMn spin valvemultilayed nanowires were electrodeposited in AAO template by the method ofdouble bath. The morphology and structure of FeMn and NiFe/Cu/NiFe/FeMnnanowires were characterized by scanning electron microscopy （SEM）, transmissionelectron microscopy （TEM）, and the elements of nanowires were analyzed by EnergyDispersive Spectrometer （EDS）. GMR of NiFe/Cu/NiFe/FeMn spin valve multilayednanowires were measured by physical property measurement system（PPMS）. Onekind of displacement GMR sensor was designed by using NiFe/Cu/NiFe/FeMnnanowires, NiFe/Cu/Co/Cu multilayer film and NiFe/Cu/Co/Cu nanowires. Theexperimental platform was constructed and the performance of the sensor was studied.SEM images showed that the FeMn alloy nanowires and NiFe/Cu/NiFe/FeMnmultilayed nanowires were highly ordered and the diameter of nanowires was80nm.The multilayered structure could be seen in the TEM image. EDS analysis showedthat the alloy layer was Fe₅₀Mn₅₀.The GMR of NiFe/Cu/NiFe/FeMn multilayed nanowires were varied greatlywith the changes of thinness of Cu, free ferromagnetic layer, pinned ferromagneticlayer and antiferromagnetic layer. Along with the increase of the thinness of Cu, freeferromagnetic layer, pinned ferromagnetic layer, the GMR was increased at first, andthen decreased. The optimum thinness of Cu is3nm, and the free ferromagnetic layeris5nm.The experimental platform of GMR displacement sensor was constructed. Thetest conditions and methods were choosed to investigate the performance of the sensor.The excellent performance of the displacement GMR sensor was got by usingNiFe/Cu/Co/Cu multilayed nanowires. The performance of the three kinds of sensor chip was changed little at different environmental temperature with good temperaturestability. The performance of GMR displacement sensor was better at lowenvironmental temperature.