The ferroelectric polarization of Y2CoMnO6 aligns along the b-axis: the first-principles calculations

TL;DR

This study uses first-principles calculations and symmetry analysis to reveal that Y2CoMnO6 exhibits ferroelectric polarization along the b-axis driven by exchange striction in its E*-AFM state, advancing understanding of multiferroicity in double-perovskites.

Contribution

It provides the first detailed microscopic explanation for magnetically induced ferroelectricity in Y2CoMnO6, highlighting the role of exchange striction and lattice distortion.

Findings

E*-AFM is the ground state in Y2CoMnO6.

Ferroelectric polarization aligns along the b-axis.

Calculated polarization reaches 0.4682 μC/cm².

Abstract

Double-perovskite A2BB'O6 oxides with magnetic B and B' ions and E*-type antiferromagnetic order (E*-AFM, i.e. the ++-- structure) are believed to exhibit promising multiferroic properties, and Y2CoMnO6 (YCMO) is one candidate in this category. However, the microscopic origins for magnetically induced ferroelectricity in YCMO remain unclear. In this work, we perform detailed symmetry analysis on the exchange striction effect and lattice distortion, plus the first-principles calculations on YCMO. The E*-AFM state as the ground state with other competing states such as ferromagnetic and A-antiferromagnetic orders is confirmed. It is revealed that the ferroelectricity is generated by the exchange striction associated with the E*-AFM order and chemically rdered Mn/Co occupation. Both the lattice symmetry consideration and first-principles calculations predict that the electric polarization aligns along the b-axis. The calculated polarization reaches up to 0.4682 uC/cm2, mainly from the ionic displacement contribution. The present work presents a comprehensive understanding of the multiferroic mechanisms in YCMO and is of general significance for predicting emergent multiferroicity in other double-perovskite magnetic oxides.