Abstract
We describe a mean-field theory of magnetic fluctuations in layered metallic materials at finite temperatures. It has a first-principles electronic structure basis and uses the spin-polarized screened Korringa-Kohn-Rostoker method and the coherent-potential approximation to describe the effects of the fluctuating “local moments” upon the electronic structure. At no stage is there a fitting to an effective classical Heisenberg model. From this disordered local moment picture we find the layer dependent paramagnetic spin susceptibility of films and multilayers above the Curie temperature which describes how the type of magnetic correlations varies layer by layer. We study thin films of Fe and Co (1–8 layers) on and embedded in nonmagnetic substrates, specifically bcc-Fe/W(100), fcc-Fe/Cu(100), and fcc-Co/Cu(100). In uncapped Fe/W(100) we find intralayer ferromagnetic correlations in all thicknesses of the iron film except in the layer nearest the W substrate in agreement with experiment. The interlayer couplings are also ferromagnetic and short ranged. There are also ferromagnetic intralayer and interlayer couplings throughout the Co films in fcc-Co/Cu(100). In the Fe/Cu(100) system the top two layers are coupled ferromagnetically and the rest antiferromagnetically. Cu capping has a profound effect upon the magnetic coupling in both Fe/Cu(100) and Co/Cu(100) with showing an oscillating behavior as a function of the cap layer thickness. In contrast there is no dramatic effect when Fe films are embedded in W(100).
- Received 21 March 2002
DOI:https://doi.org/10.1103/PhysRevB.66.094415
©2002 American Physical Society