The low-frequency noise is the most important influence on the low frequency resolution and sensitivity in tunnel junction magnetoresistance(TMR) sensors and giant magnetoresistance (GMR) sensor for the large noise power density. In this paper, We describe the 1/f noise characteristics, sources, theoretical models, testing methods and noise reduction measures for TMR sensors and GMR sensors, and the detailed physical model of 1/f noise in the tunnel junction magnetoresistive sensor is explained. By nano-simulation software Virtual NanoLab, Fe/MgO/Fe magnetic tunnel junctions (MTJs) with different thicknesses of MgO layer are studied. Their tunneling probabilities and TMR change rates are simulated and calculated, the conservative and the optimistic estimates of the Change rate of TMR are 98.1 % and 10324.55%.While the influence of MgO thickness on noise is studied through the MTJ model. To study the noise dependance on external magnetic field, an magnetic shielding equipment for noise measurement is set up, and the tests show that the noise in the magnetic shielding environment is significantly reduced.
BiOBr/Ti3C2 composite photocatalyst with highly exposed (001) facets was synthesized by hydrolysis method. Different instruments were employed to characterize the samples. The visible light photocatalytic performance of different samples were evaluated by using Rhodamine B as the target pollutant. The results show that the degradation efficiency of Rhodamine B reaches 97.1% within 60 min over BiOBr/Ti3C2 (20.0wt% Ti3C2 addidion) composite photocatalyst, which is 34.7% higher than that of BiOBr. With the introduction of layered Ti3C2, the interface between BiOBr and Ti3C2 forms the Schottky junction energy barrier, which produces effective electron traps to inhibit the combination of photogenic electron-hole pairs, and greatly improves the visible light photocatalytic activity of BiOBr. After 5 cycles, the degradation efficiency of BiOBr/Ti3C2 composite photocatalyst remains at 91.0%, showing the reliable stability. The active species capture experiment shows that superoxide radical (• O2-) is the main active species in the photocatalytic degradation of Rhodamine B, and a possible photocatalytic mechanism is proposed accordingly.
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