The ferroelectric polarization of Y₂CoMnO₆aligns along the b-axis: the first-principles calculations

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 Aantiferromagnetic 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 C/cm 2 , 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.

Magnetoelectric and structural properties ofY2CoMnO6: The role of antisite defects

“…We have established the magnetic structure composed of a collinear FM arrangement of Co 2+ and Mn 4+ moments in the xz plane with a minor AFM canting along the y direction. This paper rejects the formation of an E-type magnetic structure reported in previous papers [10,11].…”

“…Moreover, the report of a partial suppression of the electric polarization after applying a magnetic field of 5 T suggests a significant magnetoelectric coupling. This report is supported by first principle calculations that yield a magnetic ground state composed by an E-type order in competition with ferromagnetic (FM) and A-type antiferromagnetic (AFM) orderings [11]. An electric polarization of ∼4700 μC m −2 is calculated, but this value is almost two orders of magnitude higher than the experimental data obtained from pyroelectric measurements [10].…”

Magnetic order and magnetoelectric properties of R2CoMnO6 perovskites ( R=Ho , Tm, Yb, and Lu)

“…This was ascribed to the break of inversion center induced by the onset of E-type magnetic ordering and a ferroelectric ordering was expected. 11,14,17 We did not detect any evidence of spontaneous electric polarization in our samples. Instead we found thermally stimulated depolarization currents ascribed to defects in the samples.…”

“…This report is supported by first principle calculations that yield a magnetic ground state of an E-type order in competition with F-and A-type orderings. 17 However, our recent neutron diffraction study reveals that Y 2 CoMnO 6 undergoes a FM transition. No ferroelectric transition is observed but a pyroelectric effect arising from thermally stimulated depolarization currents.…”

Improper ferroelectricity at antiferromagnetic domain walls of perovskite oxides

“…Indeed, here we would like to explore if another mechanism can generate an electrical polarization in SmFeO 3 or, more generally, in rare-earth orthoferrites or rare-earth orthochromites sharing the same atomic structure and possessing magnetic ordering of the Fe or Cr spins. More precisely, we wish to determine if the finding recently made in double perovskite systems [18][19][20][21] can be generalized to SmFeO 3 and rare-earth orthoferrites or orthochromites, with quantitative formulation of polarization arisen as a result of antiferromagnetic domain anti-phase boundaries. The aims of this paper are to reveal that how magnetic domain boundaries can indeed generate a polarization (along a specific direction) in such compounds, and to provide the microscopic features and precise driving mechanisms of such polarization, by using and analyzing first-principles simulations.…”