Quantum size effect and the giant magnetoresistance in magnetic multilayers

Publisher Website
Google Scholar
Abstract
A theoretical model which accounts for the variations of the giant magnetoresistance, Δρ/ρ, with electron mean free path, L, interface roughness, r, and magnetic, tM, and normal layer, tN, thickness has been previously presented for sandwich films. It employs the quantum‐size‐effect theory of resistivity in thin films and relies on spin dependent transmission or reflection at individual layer boundaries to establish the metallic quantum‐well states. This model has now been extended (i) to films where L can be different in the magnetic, LM, and nonmagnetic, LN, layers, (ii) to an electron/atom number, n, of 0.131 as well as 1.047, and (iii) to films from sandwiches to those with as many as 64 (63) magnetic (nonmagnetic) layers. The focus is on films with relatively thin tM and tN where quantum, as distinguished from semiclassical, effects should dominate. Typical results can be summarized as follows: for tM∼tN∼10 monolayers, ML, and L’s∼70 ML, Δρ/ρ increases more rapidly as LM than LN, but this effect is reduced as one goes from sandwiches to superlattices; Δρ/ρ is approximately 50% in a superlattice with r=5 ML, which is an order of magnitude larger than in a superlattice with r=1 ML. In a sandwich the difference between r=5 and r=1 is closer to a factor of 5. In the sandwiches Δρ/ρ is smaller for n=0.131 than for n=1.05.