# Giant gigahertz optical activity in multiferroic ferroborate

## TL;DR

This paper demonstrates that samarium ferroborate exhibits a giant, intrinsic magnetodielectric effect driven by a large electromagnon with exceptional optical activity, revealing new potential for multiferroic applications.

## Contribution

It provides experimental evidence of an intrinsic giant magnetodielectric effect caused by an unusually large electromagnon in samarium ferroborate.

## Key findings

- Giant magnetodielectric effect is intrinsic in samarium ferroborate.
- Electromagnon exhibits over 120 degrees of polarization rotation.
- Effect occurs in the microwave frequency range.

## Abstract

In contrast to well studied multiferroic manganites with a spiral structure, the electric polarization in multiferroic borates is induced within collinear antiferromagnetic structure and can easily be switched by small static fields. Because of specific symmetry conditions, static and dynamic properties in borates are directly connected, which leads to giant magnetoelectric and magnetodielectric effects. Here we prove experimentally that the giant magnetodielectric effect in samarium ferroborate SmFe3(BO3)4 is of intrinsic origin and is caused by an unusually large electromagnon situated in the microwave range. This electromagnon reveals strong optical activity exceeding 120 degrees of polarization rotation in a millimeter thick sample.