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INTER-GRAIN EXCHANGE INTERACTION FOR SINGLE-PHASE NANOCRYSTALLINE Nd-Fe-B MAGNETS 总被引:1,自引:0,他引:1 下载免费PDF全文
The demagnetization curve as a function of intensity of the inter-grain exchange interaction was calculated for single-phase nanocrystalline Nd-Fe-B magnets by use of the finite-element technique of micromagnetics. Also, the strength of the exchange interaction was estimated as a function of the Nd content x for the nanocrystalline NdxFe94-xB6 magnets by comparing the above result with the experimental relation between iHc and x for the magnets. We found that the inter-grain exchange interaction decreases with the increase of x, are ≈70% and ≈60% of the inter-grain exchange interaction for x=15.5(μ0iHc≈2.0T) and x=19(μ0iHc≈2.3T), respectively. 相似文献
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The demagnetization process for a Nd2Fe14B grain covered by an α-Fe layer was studied by use of the finite element technique of micromagnetics. μ0iHc decreases with the increase of α-Fe layer thickness t. With the increase of t from 0 to 6nm, μ0iHc decreases from ~7 T to ~3.5 T when the angle between the applied field and the c-axis of the Nd2Fe14B grain is 0.5° and from ~4 T to ~1.5 T when the angle is 30° or 60°. The effect is only slightly affected by the angle between the α-Fe layer and the field direction. 相似文献
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Vortex domain structures and dc currentdependence of magneto-resistances in magnetic tunnel junctions 下载免费PDF全文
Microfabrication and the magneto-transport characteristics of the magnetic tunnel junctions (MTJs) with a spin-valve-type structure of Ta (5nm)/Ni_{79}Fe_{21} (25nm)/Ir_{22}Mn_{78} (12nm)/Co_{75}Fe_{25} (4nm)/Al(0.8nm) oxide/Co_{75}Fe_{25} (4nm)/Ni_{79}Fe_{21} (20nm)/Ta(5nm) were investigated in this paper. A series of experimental data measured with a MTJ was used to verify a magnon-assisted tunnelling model and theory. Furthermore, a micromagnetics simulation shows that the butterfly-like vortex domain structures can be formed under a current-induced Oersted field, which decreases the net magnetization values of the ferromagnetic electrodes under a large dc current (i.e., in high voltage regimes). It is one of the main reasons for the tunnel magnetoresistance ratios to decrease significantly at high voltage biasing. 相似文献
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ANISOTROPIC CHARACTERISTICS OF DEMAGNETIZATION CURVE FOR NANOCRYSTALLINE Nd-Fe-B MAGNET CALCULATED BY MICROMAGNETICS 下载免费PDF全文
The demagnetization curves for nanocrystalline Nd-Fe-B magnets of a stoichiometric composition were calculated by making use of the finite element technique of micromagnetics. The curve, especially iHc, varies in a wide range with the direction of applied field if the grain number N is taken to be small. With the increase of N, the range becomes smaller and the average of iHc decreases and approaches a limit iHc(N=∞). iHc for finite N is larger than, or at least equal to, iHc(N=∞). Jr/Js is weakly affected by N and the field direction. Jr/Js(N=∞) decreases with the increase of grain size L. These are larger than the experimental values for the Nd-rich Nd2.33Fe14B1.06Si0.21 magnets by ~0.05. iHc(N=∞) increases with the increase of L, and is close to or somewhat smaller than the experimental values of the Nd-rich magnet, as would be expected. In contrast, the curve calculated for the non-interacting grain system (Stoner-Wohlfarth model) of N≥30 depends neither on the field direction nor on N. 相似文献
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