Khalid Fatthi Eid

Spin-memory loss at 4.2 K in sputtered Pd and Pt and at Pd/Cu and Pt/Cu interfaces

We derive spin-diffusion lengths at 4.2 K in sputtered Pd and Pt of lsfPd=25−5+10 nm and lsfPt=14±6 nm, interface specific resistances of sputtered Pd/Cu and Pt/Cu of 2ARPd/Cu=0.9±0.1 fΩ m2 and 2ARPt/Cu=1.5±0.1 fΩ m2, and the amount of spin-memory loss at the Pd/Cu and Pt/Cu interfaces as δPd/Cu=0.24−0.03+0.06 and δPt/Cu=0.9±0.1. We compare our values with those from metals in similar rows of the Periodic Table, Nb for Pt and W for Pd.

Current-perpendicular-to-plane-magnetoresistance properties of Ru and Co/Ru interfaces

Recent interest in Ru and Co/Ru multilayers stimulated us to measure their properties in the current-perpendicular-to-plane (CPP) geometry at 4.2 K. For sputtered samples, we present results for the resistivity of Ru, the interface specific resistances of Cu/Ru and Co/Ru, the spin-memory-loss length lsfRu in Ru, the spin-memory-loss probability at Cu/Ru interfaces, and the spin-scattering anisotropy parameter γ at Co/Ru interfaces.

Spin-memory loss and current-perpendicular-to-plane-magnetoresistance in sputtered multilayers with Au

We derive a spin-diffusion length at 4.2 K in sputtered Au, lsfAu=35−5+65 nm, spin-memory-loss at Au/Cu interfaces, δAu/Cu=0.13−0.02+0.08, and Au/Cu interface specific resistance, 2ARAu/Cu=0.35−0.05+0.10 fΩ m2. We also show that exchange biased spin valves with Au sandwiched between Co layers produce changes in specific resistance, AΔR, comparable to those for Cu and Ag.

Enhancing current-perpendicular-to-plane magnetoresistance by adding interfaces within ferromagnetic layers

We show that adding “internal interfaces” within each Co layer can enhance both the total current-perpendicular-to-plane specific resistance, AR, and the change in specific resistance with magnetic field, AΔR, of [Py/Cu/Co/Cu]3 hybrid multilayers, AΔR by over 100%, with only a small increase in the total sample thickness. However, the growth of both AR and AΔR with the number of inserted interfaces is slower than predicted by a simple two-current series-resistor model. We provide evidence that this less rapid growth is due to spin-flipping at the Co/Cu interfaces, plus the formation of “incomplete interfaces” when the Cu layers are very thin.

Changes in magnetic scattering anisotropy at a ferromagnetic/superconducting interface

We show that some metals and alloys (Cu, Ag, FeMn, or Cu and Ag combined with each other), sputtered between ferromagnetic Co and superconducting Nb, produce no change in current-perpendicular-to-plane (CPP) magnetoresistance (MR) in a carefully designed CPP spin valve. In contrast, other metals (Ru or Au) or combinations (Cu or Ag combined with Au, Ru, or FeMn) change the CPP-MR, in some cases even reversing its sign. We ascribe the latter changes to activation of magnetic scattering anisotropies at a ferromagnetic/superconducting interface, with the differences in behavior for different metals apparently driven by differences in the strength of spin flipping when these metals are inserted between the Co and Nb layers.