Optimization The AMR Effect In NiFe Thin Films And Its Integration In Magnetic Switches

NiFe thin films material becomes the preferred material for the development of magnetic sensors because of its high Curie temperature, larger Anisotropic Magnetoresistance Effect(AMR) and relatively low price. This work aims to obtain excellent performance NiFe thin films with high AMR value, high magnetic sensitivity and low saturation field. Then the thin films were integrated onto fabricated integrated circuit. Thus a magnetoresistive sensor chip is formed, and the switching performance and temperature stability were tested.Firstly, The effects of different NiFe layer thickness to the film’s AMR value,magnetic sensitivity(Smax) and Saturation field(Hs) is studied. The results showed that with the increase of NiFe layer thickness, the AMR and Smax are both increase and then decrease after reaching the maximum value of 1.25% and 0.18 at 12 nm,but Hs decreases and then increases after reaching the minimum value of 12.05 Oe at that thinkness.Secondly, under the oblique sputtering method, the direction of NiFe thin films’ easy magnetization axis is studied.The results showed that easy magnetization axis of NiFe thin films was along the direction of the fixture tangential direction. They were aligned after annealing in the magnetic field atmosphere.Thirdly, The influence of annealing temperature and annealing time on AMR value、Smax and Hs is studied. The results showed that with the increase of annealing temperature, the AMR and Smax are both increases and then decreases after reaching a maximum value of 1.68% and 0.48 at 400 ℃, Hs decreases and then increases after reaching the minimum value of 5 Oe at 300 ℃; With the increase of annealing time, the AMR value firstly increases and then decreases at the temperature of 300 ℃, reaching a maximum value of 1.78% at 3 h. Smax value firstly increase and then decrease, reaching a maximum value of 0.65 at 5 h, Hs firstly decreases and then increases after reaching the minimum value of 4.9 Oe at 3 h.The relationship between the substrates surface roughness σ and the magnetic performance is studied. The results showed that as σ increases from 0.6nm to 1.12 nm,the AMR value decreases from 1.05% to 0.6%, Smax value decreases from 0.12 to 0.025,and Hs value increases from 15.04 Oe to 42.87 Oe. In addition, as σ increases, thesaturation magnetization(M) in the easy magnetization axis direction is gradually decreased from 1160 KA/m to 1120 KA/m, the coercive force(Hc) increases by 3.6 Oe to 6 Oe, and in the hard axis direction,there is no relationship between σ and M or Hc.Finally, We test the chips’ switching performance. The performance of our chips is comparable with similar commercial products.