Selection rules for oscillations of the giant magnetoresistance with nonmagnetic spacer layer thickness

Abstract

Oscillations of the giant magnetoresistance (GMR) with nonmagnetic spacer layer thickness are predicted in the current-perpendicular-to-plane (CPP) geometry. The methods of the quantum-well theory of the oscillatory exchange coupling are applied to the Kubo formula to derive general selection rules for the GMR oscillation periods. The selection rules are illustrated for single-orbital tight-binding and parabolic band models. They predict that the CPP GMR oscillates not only with the expected Fermi-surface period but also with additional periods determined by the potential steps between the magnetic and nonmagnetic layers.

Theory of tunneling magnetoresistance in a disorderedFe∕MgO∕Fe(001)junction

“…2,3 The real part of the perpendicular wave vector in MgO could give rise to oscillations of TMR. 2,11 However, since the MgO complex Fermi surface has no real part in a large region around the ⌫ point, this cannot be the correct explanation of the observed oscillations. Furthermore, the fact that the observed oscillations do not decrease with increasing MgO thickness is further evidence that they do not arise from the MgO complex Fermi surface.…”

Perspectives of giant magnetoresistance

“…These oscillations originate from quantum size effects and were first predicted by Mathon et al 164 for the CPP GMR within the ballistic transport regime. Using a single-band tight-binding model and the recursive approach Mathon et al predicted the presence of two types of oscillation.…”

“…We note that noticeable oscillations in the resistance at very small thicknesses, which are seen from the full circles in Fig.40, are reminiscent of the oscillations in the ballistic regime of conduction. 164 A realistic band structure of the multilayer predicts a more diverse pattern of behavior for the layer-thickness-dependent interface resistance. At a small layer thickness separating two interfaces the interface resistance can be enhanced or reduced depending on the band structure of adjacent metals.…”

Quantum oscillation of magnetoresistance in tunneling junctions with a nonmagnetic spacer

“…These oscillations show more than one period. The Fermi wave vector k F and the cut-off k-point k cp of NM are given by 2t cos(k F a) = V NM − E F − 4t and 2t cos(k cp a) = V FM− − V NM , respectively [22]. Therefore, the periods of oscillation estimated from k F = 4π/5a and k cp = 2π/3a are 5a and 3a, respectively.…”