Electromagnons in the multiferroic state of perovskite manganites with symmetric-exchange striction

TL;DR

This study investigates electromagnons in perovskite manganites with various spin structures, revealing distinct spectral features in the E-type phase and identifying a zone-edge magnon as a key contributor.

Contribution

It provides systematic experimental evidence of electromagnons in E-type manganites and links specific spectral peaks to magnon modes, expanding understanding of spin-charge interactions.

Findings

Three-peak electromagnon structure observed in E-type phase

Electromagnon frequencies show little composition dependence

Identification of a zone-edge magnon as an electromagnon component

Abstract

We have investigated electrically-active magnetic excitations (electromagnons) in perovskite manganites with the $E$-type (up-up-down-down) spin structure by terahertz spectroscopy. Eu$_{1-x}$Y$_x$MnO$_3$ (0.1$\le x\le$1) and Y$_{1-y}$Lu$_y$MnO$_3$ (0$\le y\le$1) without magnetic $f$-moments, which host collinear sinusoidal, $A$-type, cycloidal, and $E$-type spin orders, are used to examine the systematics of possible electromagnons. Three-peak structures (23, 35, 45 cm$^{-1}$) of magnetic origin show up in the $E$-type phase with little composition ($y$) dependence of frequencies, making a contrast with the electromagnons observed in the cycloidal-spin ($x\le0.8$) phases. One of these electromagnon is ascribed to the zone-edge magnon mode based on the calculated magnon dispersions.