Preparation And Characterization Of GMR Spin-valve Materials

Since the giant magnetoresistance(GMR)effect was discovered in 1988,the magnetic sensing technology based on GMR effect has attracted widespread attention.Due to the advantages of high magnetoresistance ratio,low saturation field and high sensitivity,the GMR sensors of the spin valve structure has been applied in areas of aerospace,auto-electric and automation control.The spin valve material,which its performance directly affects the sensitivity,hysteresis characteristics and working range of the sensor,is the core part of the spin valve sensor.In order to prepare high-performance spin valve film materials,the spin valve material is deeply studied in the structure design,the performance testing and the structure characteristics in this paper.This paper first introduces the research status and application prospect of GMR effect.The physical mechanism of GMR effect and working principle of spin valve material are also studied.We have designed spin valve materials with single free layer structure,composite free layer structure and synthetic antiferromagnetic pinned layer structure.Top pinned spin valve materials with single free layer structure are prepared by magnetron sputtering system on the Si substrate.The thickness of each layer in the spin valve structure was optimized,and the influence of the thickness on the performance of the material was analyzed.The influence of composite ferromagnetic free layer and synthetic antifeiromagnctic layer on the material properties of spin valve material was also studied,and the spin valve structure and preparation process were optimized.After optimization,the magnetorcsistance ratio of the spin valve material reaches 6.73%.Furthermore,the angle dependence behavior of the spin valve material is tested and analyzed by two experiments.In the first experiment,the magnetoresistance of material curves of spin valve materials are measured by applying magnetic field with a fixed angle compared to the pinning direction.It is found that the magnetorcsistancc ratio of the spin valve material is proportional to the absolute value of cosine of the direction angle of the magnetic field.In the second experiment,the resistance value of the spin valve material is tested under a fixed strength rotating magnetic field.After analyzing the data,it is found that the magnetization direction of the pinned layer in the spin valve material will obviously deviate from the original pinning direction by the effect of rotation magnetic field above 100Oe.The relationship between the deviation angle of the magnetization direction of the pinned layer and the direction angle of the rotating magnetic field is analyzed.