The Research On Magnetic Unipolar Switch Sensor Based On Giant Magnetoresistance Effect

Based on the demand of Internet of things technology development,magnetic sensor as a non-contact sensing components,has become increasingly indispensable.Among all kinds of magnetic field sensors,giant magnetoresistance(GMR)sensor based on Giant magnetoresistance has attracted the attention of researchers from all over the world because of its small size,low power consumption,stable performance and easy integration.In this study,In order to solve the problem that the field of giant magnetoresistance unipolar switch can be adjusted in a small range,a double-pinning spin valve structure is proposed,which can be easily adjusted by using the Exchange bias,the coupling field which can only be changed in a small range is replaced by an adjustable Exchange bias to meet the application requirements of a larger switching field.The research work carried out is as follows:First of all,in order to realize the wide range of switching field of magnetic unipolar switch,a double-pinned Spin Valve structure is proposed in research,which can realize the bigger adjustable range of the switch field by the Modulation of FM/AFM's Exchange bias.The structures of Ta/Ni Fe/Ir Mn/Co Fe/Cu/Co Fe/Ir Mn/Ta and Ta/Co Fe/Ir Mn/Co Fe/Ru/Co Fe/Cu/Co Fe/Ir Mn/Ta were studied in our research.Because two Exchange Bias of the Ir Mn/Co Fe bilayers on the bottom and the Co Fe/Ir Mn bilayers on the top of the bilayers are similar,it is found that the bottom pinning and the top pinning of the bilayers overlap according to the experimental results,it is difficult to realize the effective modulation of switch field.The latter is replaced by a group of conventional pinning structures,which are artificially antiferromagnetic(SAF)structures with larger Exchange bias,and by comparing the effects of SAF on the properties of double-pinning spin valve films at the top layer and the bottom layer of the structure,the double-pinning Spin Valve structures with SAF at the bottom layer and conventional pinning structure at the top layer of the structure were determined,can solve the problem of the former structure.Finally,the modulation of Brp in 70-164 Oe and Bop in 148-242 Oe can be realized by changing the thickness of the conventional pinned layer in the double-pinned spin valve in the range of 8-16 nm.Then,based on the Ta/Co Fe/Ir Mn/Co Fe/Ru/Co Fe/Cu/Co Fe/Ir Mn/Ta thin films,the fabrication and testing of single-bridge magnetic unipolar switches were carried out,the magnetic unipolar switch with open field Bop of 20 Oe and closed field Brp of 192 Oe is realized,which meets the application requirements of magnetic unipolar switch.Furthermore,the switching field can be adjusted effectively by changing the thickness of Co Fe in the conventional pinned layer in the range of 6-10 nm.Compared with the current commercial application of giant magnetoresistance unipolar switch with a maximum operating field of 80 Oe,the dual-pinned spin valve unipolar switch sensor can be used in a wider range of magnetic field applications.