Construction of high‐performance magnetic sensor based on anisotropic magnetoresistance Ta/MgO/NiFe/MgO/Ta film

Abstract

Abstract The anisotropic magnetoresistance film is an important core material for developing the magnetic sensors. Here, Ta(5)/MgO(3)/NiFe(10)/MgO(3)/Ta(3) multilayers (in nanometer) were prepared by magnetron sputtering and further applied to construct a sensor element by combining with the Wheatstone bridge. The 1/ f noise of the sensor element was greatly reduced by three orders of magnitude after annealing at 400 °C for 7200 s, which was mainly due to the significant microstructural changes during the annealing. However, when the sensor element was applied to detect the magnetic signal of a magnetic code disk with 512 N–S magnetic poles, the output voltage signal of the sensor displayed a large fluctuation of ± 0.05 V. In order to reduce the voltage fluctuation, a magnetic sensor chip by using a parallelly arranged multi‐path Wheatstone bridges and auto‐gain compensation structure was designed, and magnetic sensor elements and the high‐performance computing drive module were prepared. The output voltage fluctuation of the magnetic sensor was reduced by about 90% and approached to ± 0.005 V. These findings provide an important basis for the practical application of NiFe‐based magnetic sensing film materials.