The paramagnetic Lyddane-Sachs-Teller relation

TL;DR

This paper derives a paramagnetic analog of the Lyddane-Sachs-Teller relation, enabling optical analysis of magnetization in paramagnetic materials and introducing the concept of paramagnetic polaritons for future photonic use.

Contribution

It introduces a new relation for magnetic dipole transitions analogous to the Lyddane-Sachs-Teller relation, linking optical frequencies to static magnetization properties.

Findings

Good agreement between theory and terahertz ellipsometry measurements

Validated relation through SQUID measurements on Iron-doped Gallium Nitride

Proposes paramagnetic polaritons as potential photonic applications

Abstract

In this letter, we derive an expression for magnetic dipole transitions that is analogous to the Lyddane-Sachs-Teller relation for dielectric polar lattice vibrations. We thereby define transverse and longitudinal optical frequencies at which paramagnetic resonance and antiresonance occurs, respectively. The relation found here thus permits non-invasive optical analysis of static magnetization properties in paramagnetic materials. Validated through terahertz electron paramagnetic resonance ellipsometry and superconducting quantum interference device measurements on Iron-doped Gallium Nitride, our findings show very good agreement between theory and experiment. We term the excitations associated with the paramagnetic transitions as paramagnetic polaritons which may find use in future photonic applications