Electronic Structure, Phonons and Dielectric Anomaly in Ferromagnetic Insulating Double Perovskite La2NiMnO6

TL;DR

This study uses first-principles calculations to explore the electronic, magnetic, and phononic properties of La2NiMnO6, revealing soft phonons that couple with spins and likely cause its dielectric anomaly.

Contribution

It provides a detailed first-principles analysis linking soft phonons and spin interactions to dielectric anomalies in La2NiMnO6, a novel insight into its magnetoelectric behavior.

Findings

Existence of very soft infra-red active phonons.

Strong coupling between phonons and spins at Ni and Mn sites.

Identification of phonon modes as the origin of dielectric anomaly.

Abstract

Using first-principles density functional calculations, we study the electronic and magnetic properties of ferromagnetic insulating double-perovskite compound La2NiMnO6, which has been reported to exhibit interesting magnetic field sensitive dielectric anomaly as a function of temperature. Our study reveals existence of very soft infra-red active phonons that couple strongly with spins at the Ni and Mn sites through modification of the super-exchange interaction. We suggest that these modes are the origin for observed dielectric anomaly in La2NiMnO6.