Spin-dependent scattering of conduction electrons in Co/Cu multilayers

• We measured magnetorefractive effect (optical analogue of GMR) in Co/Cu multilayers.
• Parameters of spin-dependent scattering of conduction electrons were defined.
• Conditions are discussed to minimize scattering and to maximize MRE and GMR in Co/Cu.

The magnetotransport properties of giant magnetoresistive Co/Cu multilayers with Cu layer thickness tCutCu varied from 8 to 27 Å are studied using the magnetorefractive effect. Interfacial relaxation times τi↑(↓) and scattering probabilities Pi↑(↓), and interface scattering asymmetry γCo/CuγCo/Cu of conduction electron were obtained from the magnetoreflection in the intraband absorption region. The greatest changes of τi and Pi occur in a spin-up current channel with increasing tCutCu. Due to a size quantization of transverse component of a quasi-momentum of free electrons in Cu layers, the magnitude of τi↑ oscillates reaching the maximum values at tCutCu corresponding to the first two peaks of antiferromagnetic interlayer exchange coupling, while the τi↓ experiences only slight changes keeping low values at all thicknesses of Cu layer. It was found that condition τi↑≈τCuτCu is critical to minimize the scattering of spin-up conduction electrons at Co/Cu interface. In this case, in the region of the first peak of antiferromagnetic interlayer exchange the spin asymmetry coefficient γ≈0.86γ≈0.86, and the probability of electron scattering Pi↑ is approximately equal to 0.02, which ensures the maximum values of giant magnetoresistance and magnetorefractive effect.