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We show that the giant magnetoresistance in sputtered Ni-Fe/Cu/Ni-Fe/Fe-Mn spin-valve structures is strongly reduced by the presence of compositionally intermixed regions at the NiFe/Cu interfaces. The ultrathin intermixed layers, which are not ferromagnetic, are centers of strong spin-independent scattering, thus reducing the How of polarized electrons from one ferromagnetic layer to the other. Our results show that interfacial spin-independent scattering must be included in the theory of giant magneto resistance.Spin-dependent scattering (SDS) is widely accepted as

We present comprehensive results on the magnetoresistive properties of spin-valve sandwiches comprising glass/M(1)/Cu/NisoFe2o/Fe5OMn»/Cu, where M(1) is a ferromagnetic transition metal or alloy (Co, Ni, Ni80Fe20). We discuss the thermal variation of the magnetoresistance (AR/R) and its dependence on the thicknesses of the layers constituting the active part of the spin-value sandwich [i.e., M( 1)/Cu/N(Fe]. An almost linear decrease of b,R/R is observed between 77 and 320 K. For a given ferromagnetic material, bR /R extrapolates to zero at a temperature T"sy significantly lower than the Curie temperature, and independent of the ferromagnetic layer thickness. We have identified spin-$ and spin-$ intermixing by spin-wave scattering as responsible for the thermal decrease of the magnetoresistance. We show that the magnetoresistance arises within the "active" parts of the ferromagnetic layers of 0 thickness of about 90 A located next to the M/Cu interfaces. We give a phenomenological expression relating AR /R to the longer of the two spin-dependent mean free paths, and to current shunting in the inactive part of the sandwich. The thickness of the active region is independent of temperature.

Si/Ta/NiFe/Cu/NiFe/FeMn/Ta spin-valve layered structures were analyzed by x-ray reflectivity, before and after annealing at 240, 320, and 360 °C. Specularly reflected x-ray data were collected using a high-resolution reflectometer and were analyzed by least-squares refinement. The thicknesses of the individual layers in the NiFe/Cu/NiFe/FeMn magnetic sandwich remained essentially unchanged. With the exception of the FeMn/Ta interface, the widths of the buried interfaces increased rapidly with annealing temperature. The increase in widths at each of the NiFe/Cu and Cu/NiFe interfaces from 6.8 to 22.6 Å caused a fivefold increase in the magnetically inactive layer in NiFe and a tenfold decrease in magnetoresistance. An increase in the total film thickness with annealing temperature was found to be caused by the surface oxidation of the Ta capping layer and the growth of a Ta silicide layer between the Ta buffer layer and the Si substrate.

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The tolerance of the expected read-back signal of spin valve giant magnetoresistance based structures to varying deposition and process conditions are described. We determine if spin valves can be produced reliably, and evaluate which thicknesses and properties are most critical. First, the dependence of spin valve properties on layer thickness are experimentally determined. Next, the variation of read-back signal and transfer curve characteristics with spin valve properties is calculated from micromagnetic modeling. Finally, these are convolved with the expected reproducibility of layer thickness to obtain an effective “yield” of structures within 10% of the mean amplitude. We find that spin valves can be reliably deposited, with “yields” well in excess of 90% likely.

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