We report the magnetic, dielectric, ferroelectric and magneto-electric behaviour of the Haldane spin-chain (S=1) insulating compound, Sm2BaNiO5. It has been reported in the literature that Sm2BaNiO5 orders antiferromagnetically around (TN=) 50 K through optical spectroscopic studies [1]. It is worthwhile to note that no anomaly was reported in the temperature (T) dependent magnetization (M) data at this temperature. M(T) data however reveal a broad peak around 22 K, which was attributed to of crystal-field effect of Sm+3. Very little literature exists to understand its electrical behaviour and the possible coupling with the magnetic field. The present dielectric data shows a broad peak around 22 K, which suggests possible correlation between electric dipoles and magnetism interestingly triggered by crystal-field effect. Conventional pyroelectric measurement reveals a peak near TN, which is found to arise from thermally stimulated depolarisation current However, the bias pyroelectric measurement reveals a weak peak around 22 K, reversing its sign for the opposite polarity of electric field, indicating the onset of ferroelectricity at this temperature. This is an intriguing observation, bringing out close correlation between the magneto-electric effect and the crystal-field splitting of the rare earth ion.
References
[1] A. S. Galkin and S. A. Klimin, J. Low Temp. Phys., 185 531 (2016).