Ferroelectricity enhanced by disorder in collinear-magnetism-induced multiferroic state

Abstract

To understand the fantastic static-disorder-enhanced ferroelectricity observed in Ca3Co2−xMnxO6 compound, the multiferroic state originated from the up-up-down-down spin order in different conditions of disorder is simulated by using Monte Carlo algorithm on a three-dimensional elastic Ising model with dilution. The spin structure factor and the correlation of ionic displacements are calculated to show the detailed variations of microscopic magnetic and ferroelectric structures. It is indicated that in the pure system without disorder the frustration from the long-ranged interchain interaction disrupts the up-up-down-down spin order and the corresponding ferroelectric domain, and hence suppresses the ferroelectric polarization (P). When disorder is introduced by doping a few spin defects, the frustration can be relaxed around these defects. Then the disturbance upon ferroelectric domain is lessened and hereby P is recovered effectively. The result obtained gives a clear microscopic scenario of the static-disorder-enhanced ferroelectricity observed in Ca3Co2−xMnxO6 compound.