Spin Valve Material Optimization And Sensor Application Based On Positive And Negative Giant Magnetoresistance Effect

The discovery of GMR effect in 1988 promoted the development of Magnetoelectronics,and started the research upsurge of materials and devices based on GMR effect.Giant magnetoresistance(GMR)materials have been rapidly commercialized in the fields of storage,automobile,aerospace and industry,and have attracted extensive attention from the academic and industrial researchers.Compared with GMR multilayers,spin valve materials discovered in 1991 have the advantages of low saturation field,low coercivity and good linearity,and have been widely used in current detection,attitude navigation,position detection and other sensor systems.In this thesis,in order to obtain high-performance spin valve films to prepare high-performance sensors,a series of related research work has been carried out including the structure design and performance optimization of spin valve materials,as well as the design and sensor application system based on spin valve materials.This thesis firstly introduces the research progress of GMR materials and the background of related sensor applications,and then puts forward the research content and significance of our research work.Then,the physical mechanism of GMR effect,the typical structure and working principle of spin valve materials,and several preparation technologies are summarized.By magnetron sputtering,the spin valve films with the structure of a-Ni Fe-Co Fe-Cu-Co Fe-Ru-Co Fe-Ir Mn-Ta were fabricated on Si/Si O₂ substrate.The effects of the material selection and thickness of different functional layers on the properties of the spin valve materials were studied.After optimization,the magnetoresistance of spin valve materials is about 6.0%,the exchange bias field is about 1200 Oe,and the coercivity is 3.5 Oe.By changing the relative thickness of the two Co Fe layers in Co Fe-Cu-Co Fe SAF strucure,the performances of the spin valve materials exhibit two kinds behavior of positive GMR effect and negative GMR effect.Based on these two kinds of spin valve materials,a sensing unit with Wheatstone bridge structure was designed and fabricated.And the output of the sensing unit was tested and analyzed.Finally,the application of the spin valve sensor in angle measurement is studied.The angle sensor system includes signal acquisition,signal amplification,analog-to-digital conversion,MCU processing and LED display modules.The angle sensor system can realize the angle measurement in the range of 0-360 degrees,and the rotation direction can be distinguished.The results show that the spin valve sensor has potential application prospect in angle measurement system.