Multiferroicity and magneto-electric effect in Gd2BaNiO 5

Abstract

We report the observation of electric polarization in the magnetically ordered state of the Haldane chain compound, Gd2BaNiO5, with strongly correlated magnetic and dielectric properties. The results of dc magnetic susceptibility and heat capacity measurements indicate two magnetic transitions, one corresponding to the anti-ferromagnetic order at TN ? 55 K and the other to spin-reorientation transition at TSR ? 24 K. The dielectric permittivity (?r') and loss (tan?) also exhibit anomalies in the vicinity of TSR and T N, respectively. Below the spin-reorientation transition, concurrently magnetic-field-induced spin-flop and the meta-electric transitions are observed at a critical magnetic field in isothermal magnetization and magneto-dielectric results, respectively. Another interesting finding is that ??r' (=(?r'(H)-?r' (0))/?r' (0)) changes its sign at the critical magnetic field. The origin of the observed magneto-electric effect is discussed on the basis of spin-phonon coupling. � 2014 AIP Publishing LLC.