Giant Magnetoelectric Effect in Antiferromagnetic BaMnO3-\delta and Its Derivatives

TL;DR

This study reports a giant magnetoelectric effect in antiferromagnetic BaMnO3-elta and its derivatives, showing large dielectric constant enhancements near the Ne9el temperature, with tunable properties via doping.

Contribution

It demonstrates a high-temperature magnetoelectric effect in BaMnO3-elta derivatives and shows how doping alters magnetic and dielectric properties significantly.

Findings

Dielectric constant increases over tenfold near Ne9el temperature.

Li and K doping drastically change magnetic and dielectric behaviors.

A 3% Li substitution raises dielectric constant to 2500 near Ne9el temperature.

Abstract

Hexagonal perovskite 15R-BaMnO2.99 with a ratio of cubic to hexagonal layers of 1/5 in the unit cell is an antiferromagnetic insulator that orders at a N\'eel temperature TN = 220 K. Here we report structural, magnetic, dielectric and thermal properties of single crystal BaMnO2.99 and its derivatives BaMn0.97Li0.03O3 and Ba0.97K0.03MnO3. The central findings of this work are: (1) these materials possess a usually large, high-temperature magnetoelectric effect that amplifies the dielectric constant by more than an order of magnitude near their respective N\'eel temperature; (2) Li and K doping can readily vary the ratio of cubic to hexagonal layers and cause drastic changes in dielectric and magnetic properties; in particular, a mere 3% Li substitution for Mn significantly weakens the magnetic anisotropy and relaxes the lattice; consequently, the dielectric constant for both the a- and c-axis sharply rises to 2500 near the N\'eel temperature. This lattice softening is also accompanied by weak polarization. These findings provide a new paradigm for developing novel, high-temperature magnetoelectric materials that may eventually contribute to technology.