Magnetoelectric memory in reentrant frozen state and considerable ferroelectricity in the multiferroic spin-chain compound Sm2BaNiO5

Abstract

We report intrinsic memory effect in magnetization and dielectricity for the spin-chain compound ${\mathrm{Sm}}_{2}{\mathrm{BaNiO}}_{5}$, pointing the cooperative glassy response below $\ensuremath{\sim}8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Signature of anomaly around 8 K is verified by the magnetization, heat capacity, dielectric permittivity, magnetostriction, and structural parameters as obtained from the synchrotron diffraction studies. Intriguingly, the memory effect is observed well below the magnetic and ferroelectric ordering temperatures, pointing to a reentrant frozen state. Ferroelectricity emerges above antiferromagnetic N\'eel temperature at 45 K. For 4.5 kV/cm poling field the spontaneous electric polarization attains the value of 1300 $\ensuremath{\mu}C/{\mathrm{m}}^{2}$, that is the highest value in the ${R}_{2}{\mathrm{BaNiO}}_{5}$ series. Synchrotron diffraction studies confirm that ferroelectricity emerges due to structural transition from the centrosymmetric $Immm$ to a noncentrosymmetric $Imm2$ space group. Magnetoelectric coupling is significant and scales linearly to the squared magnetization as described by the Ginzburg-Landau theory.