Spin-charge-lattice coupling in RMn2O5 multiferroic oxides

Orateur : Sumanta CHATTOPADHYAY (LPS, Orsay)

Recently, a magnetically frustrated oxide family with general formula RMn2O5 (R = rare earth, Bi, Y) is drawing considerable attention due to the fact that it ex hibits spin induced ferroelectricity below 40±5 K with an extremely large magnetoelectric coupling. In this multiferroic family, the origin of the large magnetoelectric coupling has been thoroughly studied especially for the members having small R3+ ions. However, the real microscopic origin of the magnetically driven ferroelectricity is still a matter of great debate. In addition, understanding about the influence of the R3+ ions on the magnetic and electric orders is not clear and further investigations are required to settle this issue. In this context, studies on the RMn2O5 compositions with large R3+ ions could provide crucial information to clarify these ambiguous issues. In this presentation, the focus will predominantly be on a particular member of the RMn2O5 series viz. NdMn2O5. The reasons for choosing this particular composition are twofold. It represents an RMn2O5 compound with large R3+ ion and it lies in between the paraelectric PrMn2O5 and the ferroelectric SmMn2O5 as far as the compositional phase diagram is concerned. With the help of bulk magnetization, heat capacity, electric polarization, X-ray diffraction, and neutron diffraction data, we would like to describe the multiferroic and the structural properties of this interesting compound. Whenever necessary, comparisons among NdMn2O5 and other typical RMn2O5 compositions will be presented to have a broad overview on this exotic multiferroic series. To address the ambiguous issue regarding the origin of the ferroelectrity in the RMn2O5 series, we would also like to discuss about our recent results of the single crystal X-ray diffraction measurements performed at 300 K on various multiferro ic members of this family of compounds. These results clearly reveal that an electric polarization can be present even at room temperature in the paramagnetic phase of the RMn2O5 oxides [1].

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