Magnons in Ferromagnetic Metallic Manganites

TL;DR

This review discusses how inelastic neutron scattering reveals complex magnon behaviors in ferromagnetic manganites, highlighting the interplay of charge, spin, orbital, and lattice phenomena affecting their magnetic excitations.

Contribution

It provides a comprehensive overview of magnon dynamics in ferromagnetic manganites, emphasizing the unusual softening and damping phenomena near the zone boundary.

Findings

Magnon softening and damping observed near the Brillouin zone boundary.

Anomalous magnon behaviors linked to strong Jahn-Teller distortions.

Evidence of cooperative excitations involving multiple degrees of freedom.

Abstract

Ferromagnetic (FM) manganites, a group of likely half-metallic oxides, are of special interest not only because they are a testing ground of the classical doubleexchange interaction mechanism for the colossal magnetoresistance, but also because they exhibit an extraordinary arena of emergent phenomena. These emergent phenomena are related to the complexity associated with strong interplay between charge, spin, orbital, and lattice. In this review, we focus on the use of inelastic neutron scattering to study the spin dynamics, mainly the magnon excitations in this class of FM metallic materials. In particular, we discussed the unusual magnon softening and damping near the Brillouin zone boundary in relatively narrow band compounds with strong Jahn-Teller lattice distortion and charge/orbital correlations. The anomalous behaviors of magnons in these compounds indicate the likelihood of cooperative excitations involving spin, lattice, as well as orbital degrees of freedom.