| In this article, the development, uses and mechanism of several kinds of magnetoresistance effect are introduced generally and simply. The development of magnetoresistance effect from the permalloy films is also introduced. The ternary alloy NiFeNb is used as the new seed layer and the (Ni82Fe18)1-xNbx (d)/Ni82Fe18 (t)/Ta(30A) films with different Nb atom concentration x in the seed layer, NiFeNb thickness (d) and NiFe thickness (t) are prepared. Some samples are annealed. The Nb atom concentration in the seed layer and the microstructure, MR curves and hysteresis loops of samples are measured. Variation of the resistivity and MR with the x, d and t are fit non-linearly with Origin Software. And the results of samples unannealed and annealed are compared. In the other hand, the grain sizes are computed with Sherrer Formula and the X-parameter tables. Then from the microstructure gained, we analyses the reason why the resistivity and MR vary with x, d, and t with the spin-relevant scattering theory, semiclassical model used by Th. G. S. Rijks which similar to Funchs-Jondheimer theory and metallic conductivity theory. In the last part of this article we probe the mechanism that the new seed layer cause influence on the microstructure of the permalloy films, which results in the variation of P and MR with x, d and t based on our microscope model built from the solid state physics theory.In short, our main studies are followed:Firstly, the microstructures of the permalloy films prepared with different conditions are measured. Although different conditions, in permalloy films growing on the new seed layer NiFeNb, the single and striking fcc (111) peaks are observed, which is the direction of easy magnetization. However, other peaks are not observed in the films unannealed even if the NiFe(200) and Ni,Fe(200) weak peaks in the permalloy films post-annealed are found. The grain sizes of our samples computed are in the 28.63nm~47.72nm. And with different conditions, the grain sizes are different.Secondly, the variations of P and MR with x, d and t are studied in particular and the correspond results are followed. 1 P and MR have a maximum if x=27.1% and x=24.4% respectively, p and MR decrease deeply near the correspond maximum. If x>33% and x<23% P is almost stable and x>32% and x<20.5% MR is almost stable. 2 p decreases with the increase of NiFe thickness t non-linearly, but if 27.5%40nm, the P is almost stable. In the otherhand, MR increases with t non-linearly and if t>40nm, MR is almost stable. 3 P decreases with the seed layer thickness d non-linearly, but the tendency decreases slowly till the minimum is observed if d=4.3nm. Then P increases slowly and is stable if d>6.0nm. MR also decrease with d, but the tendency decreases and MR is stable if d>3.94nm.4 post-annealing results in increasing of P in some degree and the maximum enchancement is 14.5%, which attributes to lower current shunting in permalloy sensors. Post-annealing enchances MR of the permalloy films very much and the maximum enchancement is 108%. However, the post-annealing temperature is only 200C, which can be satisfied easily by the common technique. This will accelerate uses of the permalloy films in the MR sensors.Thirdly, from microstructure of samples, we analyses the reason why P and MR vary with x, d and t with semi-classical model used by Th. G. S. Rijks which similar to Funchs-Jondheimer theory, the spin-relevant scattering theory and metallic conductivity theory. Our conclusion is that the different grain sizes attributing to different intrinsic scattering and scattering at the grain boundaries or surfaces, different texture and differently destroying sphere-symmetry of conduction electrons cause different P and MR of the permalloy films.Fourthly, variation of P and MR with x, d and t are fit non-linearly with Origin software and the quantitive variations formula of p and MR with x, d and t are found approximately.Fifthly, we build the microscopic model with the roug...
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