Magnetic Anistropy due to the Casimir Effect

TL;DR

This paper investigates how the Casimir effect induces magnetic anisotropy in ferromagnetic materials near non-magnetic plates, with the anisotropy's nature depending on the optical properties and orientation of the plates.

Contribution

It demonstrates how the Casimir interaction causes magnetic anisotropy, influenced by optical anisotropy and interplate distance, providing numerical results for various material combinations.

Findings

Out-of-plane anisotropy with isotropic plates

In-plane anisotropy with uniaxial plates

Anisotropy depends on interplate distance

Abstract

We consider the Casimir interaction between a ferromagnetic and a non-magnetic mirror, and show how the Casimir effect gives rise to a magnetic anisotropy in the ferromagnetic layer. The anisotropy is out-of-plane if the non-magnetic plate is optically isotropic. If the non-magnetic plate shows a uniaxial optical anisotropy (with optical axis in the plate plane), we find an in-plane magnetic anisotropy. In both cases, the energetically most favorable magnetization orientation is given by the competition between polar, longitudinal and transverse contributions to the magneto-optical Kerr effect, and will therefore depend on the interplate distance. Numerical results will be presented for a magnetic plate made out of iron, and non-magnetic plates of gold (optically isotropic), quartz, calcite and barium titanate (all uniaxially birefringent).