Unusual beats of the perpendicular-current giant magneto-resistance and thermopower of magnetic trilayers

TL;DR

This paper investigates unusual oscillatory behaviors in giant magnetoresistance and thermopower in magnetic trilayers, revealing long-period beats and phase differences, using a theoretical tight-binding model and Green's function calculations.

Contribution

It introduces a theoretical analysis of oscillations and beats in GMR and TEP in magnetic trilayers, highlighting non-RKKY long-period oscillations and phase differences.

Findings

Long-period beats in GMR and TEP oscillations are observed.

TEP oscillations are more pronounced and have different phases compared to GMR.

The long-period oscillations are of a non-RKKY type.

Abstract

Oscillations of the giant magnetoresistance (GMR) and thermo-electric power (TEP) vs. both the thickness of the non-magnetic spacer and also that of the ferromagnetic slabs are studied in the current-perpendicular-to-plane (CPP) geometry of magnetic trilayer systems, in terms of a single-band tight-binding model without impurities. The spin-dependent conductance has been calculated from the Kubo formula by means of a recursion Green's function method and the semi-infinite ideal-lead wires trick. Additionally the TEP is obtained directly from Mott's formula. In general, the thickness oscillations of the GMR and the TEP may have just one or two (short and long) oscillations. The long period, related to spectacular beats, is apparently of non-RKKY type. The TEP oscillations are strongly enhanced with respect to those of the GMR, have the same periods, but different phases and a negative bias.