Study On The GMR Properties Of [NiFe/Cu/Co/Cu]_n Multilayered Nanowires

The important structure for studing the CPP-GMR is multilayered nanowires. With the development of preparation technology and research of performance, multilayered nanowires will become an important impetus for the new changes of the Magneto-Electronics.Ordered NiFe/Cu/Co/Cu, NiFe/Cu and Co/Cu multilayered nanowires were electrodeposited into the pores of AAO membranes using dual-bath. The morphology, structure, magnetic properties and GMR of the nanowires were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), vibrating sample magnetometer(VSM),physical property measurement system(PPMS), respectively.SEM images showed that nanowires were highly ordered. The multilayered structure could be seen in the TEM images. SAED showed that NiFe was polycrystal structure, Co was hcp(100) structure. The growthrate of NiFe was 1.167nm/s, Cu was 0.800nm/s, and Co was 1.400nm/s.The magnetic property and CPP-GMR of NiFe/Cu/Co/Cu nanowires were varied greatly with the changes of diameter, annealing temperature and period. Along with the increase of the diameter, the magnetic property and CPP-GMR increased at first, and then decreased, with the optimum diameter of 80nm.The study of the effects of annealing on the magnetic property and CPP-GMR showed that low temperature(≤300°C) was beneficial to preferred growth of the crystal and reduction of the interface roughness, while high temperature(400°C,500°C) was adverse. The performance of nanowires were best when 300 cyclic period, however, reduced with the increase of the period, because of the aggravation of interlayer dislocation, defects, air pore and impurities.The study of magnetic property and CPP-GMR of NiFe/Cu, Co/Cu nanowires by changing the layer thickness showed that VF model was validated, and the experimental results proved that in order to getting multilayer nanowires with excellent performance, each layer thickness of metal should be maintained within spin diffusion length (SDL), including that NiFe layer thickness should be 2~5nm, Co layer thickness should be 10~15nm, and Cu layer thickness should be 7~50nm. One kind of displacement GMR sensor was designed using NiFe/Cu/Co/Cu nanowires. And the experimental platform was constructed, the test conditions and methods were maken sure to investigate the performance of the sensor.