P. A. Schroeder

Two-channel analysis of CPP-MR data for Ag/Co and AgSn/Co multilayers

Abstract We present a 2-channel model for the magnetoresistance of a magnetic multilayer with the current flowing perpendicular to the layer planes (CPP-MR), and show that the model fits previous data on Ag/Co and new data on AgSn/Co multilayers better than our previous simple series resistance model. The 2-channel model supports the conclusions previously reached for Ag/Co, and permits a determination of the spin-orientation-dependent parameters α Co = 2.9(+0.5, -0.3) and α Ag / Co = 12(+5, -2).

Giant magnetoresistance with current perpendicular to the multilayer planes

Abstract We review recent progress in measuring giant magnetoresistance in magnetic multilayers with the current flowing perpendicular to the multilayer planes (CPP-MR), and present new data for Co/Cu and Co/Ag multilayers.

Giant magnetoresistance with current perpendicular to the layer planes of Ag/Co and AgSn/Co multilayers (invited)

A two‐channel model of electronic conduction is shown to provide a satisfactory description of the magnetoresistances of Ag/Co and AgSn/Co multilayers with the current flowing perpendicular to the layer planes. A combination of data for as‐prepared samples at magnetic field H=0 (for which the magnetization M≊0), and for the same samples in the ferromagnetically ordered state, is used to extract ‘‘best’’ spin‐orientation‐dependent parameters of αCo=2.9(+0.5,−0.3) and αCo/Ag=12(+5,−2) from Ag/Co data and αCo=2.4(+1,−0.7) and αCo/AgSn=11(+7,−4) from AgSn/Co data.

Magnetic multilayers: oscillatory interlayer exchange and giant magnetoresistance

Abstract We illustrate our presentation and discussion of the interlayer exchange and magnetoresistance properties in magnetic multilayers with experimental data on Fe/Cr, Co/Cu and Fe/Cu.

Magnetoresistance of Co-Based multilayered structures

Abstract Magnetoresistance measurements have been made on sputtered multilayerd films of Ag/Co and Cu/Co. Magnetoresistances as high as 16% at 4.2 K have been measured in the field range where the magnetization reverses. The results are ascribed to the partial antiparallel arrangement of the magnetizations in alternate Co layers.

Giant magnetoresistance in Ag/Co and Cu/Co multilayers with very thin Co layers

Abstract The magnetoresistances (MR) of Ag/Co multilayers with fairly thick Co layers ( t Co ⩾1.5 nm) and relatively thin Ag layers ( t Ag ⩽3 nm) have been found to be much smaller than those for the sister Cu/Co series. Recently, however, Araki et al. reported very large MRs in Ag/Co multilayers with very thin Co layers ( t Co =0.6 nm) and sufficiently thin Ag layers. In this paper we provide additional data that expand and generally confirm Arakis observations, but lead us to propose that our Ag/Co samples with very thin layers are intermediate between multilayers and granular, with the smaller MRs for large t Co and the larger MR values for small t Co being due to a change in continuity of the Co layers. Comparative results are also presented for Cu/Co multilayers.

Superconductor/ferromagnet boundary resistances

Measurements of 2RbA, twice the boundary residual resistance times the cross-sectional area, for superconducting/ferromagnetic (S/F) boundaries in sputtered sandwiches yield values (in f Omega m2) of (6.1+or-0.3) for Nb/Co, (4.8+or-0.6) for Nb/Ni and (12.4+or-0.7) for NbTi/Co. These values are similar to those previously reported for superconducting/normal (S/N) boundaries in foil-based sandwiches, and smaller than predicted by the standard model.

Inverse CPP-GMR in (A/Cu/Co/Cu) multilayers (A=NiCr, FeCr, FeV) and discussion of the spin asymmetry induced by impurities

We present CPP-GMR experiments on a series of multilayers of the type (A/Cu/Co/Cu)×N where A is a layer of NiCr, FeCr, or FeV alloys with concentrations of Cr or V between 2.5 and 30 at. %. The inverse GMR effects we observe can be accounted for by the opposite scattering spin asymmetries in Co (positive spin asymmetry) and A (negative spin asymmetry). As the spin asymmetry in A is positive for interface scattering and negative for bulk scattering, the inverse GMR is observed only for thicknesses greater than one at which interface and bulk scattering compensate. We determine the magnitude and sign of the spin asymmetry coefficients, and we notice the agreement with previous data on dilute alloys and with theoretical calculations.

How predictable is the current perpendicular to plane magnetoresistance? (invited)

Prior measurements of the current perpendicular to the layer planes (CPP) resistances, taken on Co/Cu/Py/Cu (Py=Ni84Fe16) multilayers with a single pair of Co and Py thicknesses, are extended to three additional pairs of thicknesses. The same parameters, obtained from independent measurements on Co/Cu and Py/Cu multilayers that fit the original pair reasonably well, fit the three new pairs almost as well, from which we conclude that there is substantial predictability in the CPP magnetoresistance (MR). Because the predictability is not perfect, we examine the extent to which we can improve the fits to the Co/Cu/Py/Cu data by varying the Py/Cu and Co/Cu parameters within their uncertainties, without substantially weakening the fits to the original Co/Cu and Py/Cu data. We conclude by presenting the first CPP‐MR measurements on Co/Ag/Py/Ag multilayers. The data are similar to those for Co/Cu/Py/Cu multilayers, but the Co/Ag/Py/Ag MRs are noticeably larger.

Magnetic states of magnetic multilayers at different fields

The resistance of an as‐sputtered magnetic multilayer in zero applied magnetic field can be considerably different from the maximum resistance measured after the multilayer has been cycled to above its saturation field. We examine the relation between these two resistances in some Ag/Co, Cu/Co, and Cu/NiFe multilayers, and its implications for interpreting giant magnetoresistance.