Based On Spin Valve Magnetic Encoder

Spin valve magnetoresistance encoders with its high resolution, fast response and easily integrate are widely used in the detection of mechanical speed, angle, distance and count areas, this paper is around the international research focus. In this dissertation, spin valve film characteristic and its application have been studied.Firstly, GMR effect was introduced, including the definition and theory model of GMR, exchange bias of the ferromagnetic/anti-ferromagnetic bilayers; For spin valve Si/Ta/CoFe/Cu/CoFe/IrMn/Ta, affects of the free layer, non-magnetic layer, the pinned layer and anti-ferromagnetic layer thickness on the properties of spin valve mechanism are compared researched, spin valve structure " Ta(10nm)/CoFe(6nm)/Cu(8nm)/CoFe (4nm)/IrMn(13nm)/Ta(5nm)" has the best performance:GMR=2.53%, Hex=517Oe, while excellent performance GMR=4.67%of the spin valve is also prepared without the Cu buffer layer; Furthermore, impacts of NiFe layer in the composite free layer on the GMR and coercivity are researched. Then, for application in magnetic rotary encoder, analysis and layouts of single strip sensors, three-terminal sensors and Whiston bridge sensors are performed. Ultilizing excellent performance spin valve film, these sensors are fabricated using semiconductor process. The magnetic response of the sensors is tested systematically.Finally, designed and manufactured signal detection circuit, the magnetic rotate encoder system is assembled, the circuit has the following features:display of the frequency and speed, adjustable motor speed, adjustable sensors current supply. Test results show that:the sensors output are neatly, and can detect the magnetic field; the circuit can be very accurate, the error is very small only 0.1%; the drum and sensors distance and drum rotational speed have important implications on sensor's output signal; when the two-phase input signals with 90 degrees difference, the exact angle of each pulse represents 1.8°.