Regensburg 2002 – wissenschaftliches Programm

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MA: Magnetismus

MA 17: Exchange Coupling

MA 17.5: Vortrag

Donnerstag, 14. März 2002, 16:15–16:30, H22

Long-range magnetic interactions due to the Casimir effect — •Patrick Bruno — Max-Planck-Institut für Mikrostruturphysik, Weinberg 2, O6120 Halle, Germany

One usually considers that there exists essentially two kinds of magnetic interactions between magnetic moments or magnetized bodies: (i) the magnetostatic dipole-dipole interaction, and (ii) the electron-mediated exchange interaction.

Here, I point out that there exists a further (so far overlooked) mechanism of magnetic interaction, which results from the zero-point quantum fluctuations of the electromagnetic field (Casimir effect). The Casimir magnetic interaction between magnetic metallic layers separated by vacuum (or by a dielectric) has been calculated in the limit of large interlayer distance D and is found to decay as D⁻⁴.

In view of the fact that the interlayer exchange interaction decreases exponentially with D for a dielectric spacer and that the interlayer magnetostatic interaction is essentially zero when the layers are homogenously magnetized, the new Casimir magnetic interaction (although very small) is therefore the dominant magnetic interlayer interaction for sufficiently large distances, due to its long-range character. The detection of this new fundamental effect sets a new challenge in experimental magnetism.