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

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Abstract
Oscillations of the giant magnetoresistance (GMR) and thermoelectric power (TEP) vs both the thickness of the nonmagnetic spacer and also that of the ferromagnetic slabs are studied in the current-perpendicular-to-plane 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 the well-known Onsager relations. 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-Rudermann-Kittel-Kasuya-Yosida 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. © 1996 The American Physical Society.
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