We present careful experiments on the multiferroicity in Ca 3 CoMn 0.92 O 6 by Fe substitution of Mn. It is revealed that a proper Fe substitution modulates the Co/Mn spin order, favoring the ferroelectricity. The multifold interactions between the intra-chain spins and inter-chain spins are analyzed. It is suggested that the Mn deficiency and Fe substitution can break the inter-chain interactions to some extent, resulting in the delicate competition between these mutual interactions. The modulation of the ionic (charge) disorder and spin frustration order is the core physics for improving the ferroelectric performance. V C 2013 AIP Publishing LLC.

We investigate the effects of slight Dy/Mn off-stoichiometry on the multiferroic behaviors of DyMnO3 (Dy1−xMn1+xO3). It is revealed that the distorted lattice structure and ferroelectric property exhibit higher stability against the Mn deficiency than the Dy deficiency. Since the electric polarization includes the contributions from the Mn-Mn and Dy-Mn interactions, the measured polarization exhibits different dependence on the Mn deficiency from that on the Dy deficiency. The present work suggests that the Dy/Mn off-stoichiometry is detrimental to the ferroelectricity, owing to the modulated spin interactions and reshuffled spin frustration.