Manipulation of Dy-Mn coupling and ferrielectric phase diagram of DyMn2O5: The effect of Y substitution of Dy

Abstract

DyMn2O5 is an extraordinary example in the family of multiferroic manganites and it accommodates both the 4f and 3d magnetic ions with strong Dy-Mn (4f-3d) coupling. The electric polarization origin is believed to arise not only from the Mn spin interactions but also from the Dy-Mn coupling. Starting from proposed scenario on ferrielectricity in DyMn2O5 where the exchange-strictions associated with the Mn3+-Mn4+-Mn3+ blocks and Dy3+-Mn4+-Dy3+ blocks generate the two ferroelectric sublattices, we perform a set of characterizations on the structure, magnetism, and electric polarization of Dy1-xYxMn2O5 in order to investigate the roles of Dy-Mn coupling in manipulating the ferrielectricity. It is revealed that the non-magnetic Y substitution of Dy suppresses gradually the Dy3+ spin ordering and the Dy-Mn coupling. Consequently, the ferroelectric sublattice generated by the exchange striction associated with the Dy3+-Mn4+-Dy3+ blocks is destabilized, but the ferroelectric sublattice generated by the exchange striction associated with the Mn3+-Mn4+-Mn3+ blocks remains less perturbed, enabling the ferrielectricity-ferroelectricity transitions with the Y substitution. A phenomenological ferrielectric domain model is suggested to explain the polarization reversal induced by the Y substitution. The present work presents a possible scenario of the multiferroic mechanism in not only DyMn2O5 but probably also other RMn2O5 members with strong 4f-3d coupling.

Ferrielectricity in DyMn2O5: A golden touchstone for multiferroicity of RMn2O5 family

“…17(a) to 17(f ), respectively, 50 with several clear features in terms of ferroelectricity. First, the sharp I pyro peaks at $ T Dy and $ T N1 for x ¼ 0 become gradually suppressed as x > 0:05 until x ¼ x c $ 0:13 where the peak reversal occurs, signing the polarization reversal.…”

“…50 The Y 3þ ionic radius ($ 0.090 nm) is slightly smaller than Dy 3þ ($ 0.091 nm), and the Y substitution allows the induced lattice distortion as small as possible. Nevertheless, the Dy-Mn coupling and Dy-Dy interactions can be substantially manipulated by the substitution, and the direct consequence is gradual suppression of the P DM sublattice but the P MM sublattice remains less perturbed.…”

“…18). 50 Each domain is denoted by one square dot, and the aligned squares constitute the P DM sublattice (top row) and P MM sublattice (bottom row). The Y substitution damages some P DM domains so that the local P DM ¼ 0 (white squares) while the P MM -domains may be reversed by E pole , as labeled by the orange squares, and thus the local P MM > 0.…”

“…34 The subsequent Mn-site and Dy-site substitution experiments were designed to check this framework. 49,50 In this mini-review, we intend to present all our data on the multiferroicity of DyMn 2 O 5 in an integrated package, eventually revealing the FIE nature of DyMn 2 O 5 . The remaining part is organized as follows.…”

“…Several aspects were carefully investigated, addressing the pure, Mn-site substituted, and Dy-site substituted DyMn 2 O 5 . 49,50 The major features associated with the ferrielectricity of pure DyMn 2 O 5 were sorted out. Our strategy was to start from these features and propose a phenomenological framework.…”