Magnetoresistance of FeCo Nanocontacts With Current-Perpendicular-to-Plane Spin-Valve Structure

Spin accumulation and magnetoresistance of a CPP‐GMR system with a current confined path

“…We solve the Laplace and Poisson equations for electrochemical potentials in the CCP structure by using the finite element method. Figure 1(b) shows the MR ratio of the CCP structure as a function of the contact width w. The MR ratio increases with decreasing w, which is consistent with the experimental results of the CCP-CPP-GMR systems [5,6]. However, it should be noted that the enhancement of the MR ratio due to the CCP structure occurs even when the contact width w is much larger than the spin diffusion length λ (= 12 nm).…”

“…We show that the MR ratio is enhanced for the narrow contact, which is consistent with the experimental results [5,6]. We also show that the enhancement of the MR ratio can be explained by considering the difference between characteristic lengths of geometrical resistance and that of interfacial resistance due to spin accumulation.…”

“…They showed that the MR ratio increases with increasing the RA value, which means that the MR ratio is enhanced for the system with narrow metallic channels. The similar enhancement of the MR ratio due to the CCP structure containing a domain wall was also reported by Fukue et al [6]. They discussed the enhancement of the MR ratio due to the CCP structure by introducing the effective circuit model.…”

“…Since the area of the region (i) and (iii) decreases with increasing the angle 0 θ , the MR ratio of 0 θ = 0.125π (0.375π) is more (less) enhanced than that of 0 θ = 0.25π. For real CCP-CPP-GMR systems [5,6], the regions (i) and (iii) corresponds to the region between the two successive metallic channels. Therefore, the charactristic lengths which dominate the enhancement of the MR ratio is the spin diffusion length and distance between two successive metallic channels.…”

Characteristics of microwave oscillations induced by spin transfer torque in a ferromagnetic nanocontact magnetoresistive element

“…2 In the present study, we investigate microwave oscillations in a spin-valve ͑SV͒ structure we developed by ourselves, which has an FeCo-AlO x nano-oxide layer ͑NOL͒ as the spacer layer. 3 This SV structure has a relatively high MR ratio of 7%-10% at a resistance areal product ͑RA͒ of 0.5-1.5 ⍀ m 2 . The NOL has many metallic conductive channels with 1-2 nm in diameter, which are embedded in an ultrathin ͑ϳ1 nm͒ oxidized insulator.…”