Exchange coupling between magnetic layers across non-magnetic superlattices

Abstract

The oscillation periods of the interlayer exchange coupling are investigated when two magnetic layers are separated by a metallic superlattice of two distinct non-magnetic materials. In spite of the conventional behaviour of the coupling as a function of the spacer thickness, new periods arise when the coupling is looked upon as a function of the number of cells of the superlattice. The new periodicity results from the deformation of the corresponding Fermi surface, which is explicitly related to a few controllable parameters, allowing the oscillation periods to be tuned.

Exponential behavior of the interlayer exchange coupling across nonmagnetic metallic superlattices

“…In their simplest form they correspond to the RKKY criterion, which states that the periods are given by critical spanning wave vectors along the growth direction linking two points of the bulk spacer FS with antiparallel velocities [4]. Recently, it has been suggested that the periods of J across non-magnetic metallic superlattices can be altered in a controllable way by changing the superlattice composition, and, hence, its FS [11]. In this letter we show that it is possible to find an exponentially decaying J(N ) across non-magnetic metallic superlattices.…”

“…We have calculated J as a function of the number of atomic planes in the spacer. However, as far as the periods are concerned, it is only when probed at regular intervals of the supercell size (N s = N A + N B atomic planes) that the coupling reflects the structure of the spacer superlattice FS [11]. Therefore, to highlight the oscillation periods which are associated with the superlattice FS, when we show our calculated results for J(N ) we indicate one sub-set of N-values that are equally spaced by the supercell size N s .…”

Ab Initio Theory of the Interlayer Exchange Coupling

“…The particular case of n A = n B = 1 corresponding to an (001)-stacking of an ordered fcc-CuAu alloy was already treated on a firstprinciples level [22]. The more general case, (n A , n B > 1), which corresponds to artificially grown superstructures, was treated only within a simple oneband model [44]. In both cases, new periodicities (in comparison with the spacers consisting from pure A or B metals) arise with an increasing number of repetitions.…”