Kiran Singh, Tathamay Basu, S. Chowki, N. Mahapotra, K. Iyer, P. L. Paulose, E. V. Sampathkumaran
We report the results of various measurements, namely magnetization, complex dielectric permittivity and electric polarization (P) on Dy2BaNiO5 as a function of temperature (T) and magnetic-field (H), apart from heat-capacity (C), with the primary motivation of exploring the existence of magnetoelectric (ME) coupling among Haldane spin-chain systems. The M(T) and C(T) data establish long range magnetic ordering at 58K. The most noteworthy observations are: (i) Distinct anomalies are observed in dielectric constant (e') vs T and loss (tandelta) vs T at different temperatures, i.e. 12.5, 30, 50 and 58K, tracking magnetization (M); (ii) at low temperatures, three magnetic-field-induced transitions are observed, as inferred from isothermal M vs H and e' vs H and the critical magnetic fields Hc1, Hc2 and Hc3 are 6, 40 and 60 kOe, respectively. The magnetic-field-induced transitions at Hc2 and Hc3 at low T (<10K) exhibit a weak but a clear hysteresis which indicates first-order nature of these transitions. These T- and H-induced transitions are attributed to the rotation of Ni2+ magnetic moments towards the direction of Dy3+ moments. The appearance of polarization in the magnetically ordered state reveals magnetism-induced ferroelectricity in this compound. These results establish that this compound is a new multiferroic material among spin = 1 (nickel containing) compounds with successive magnetic transitions and strong magnetoelectric coupling.
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http://arxiv.org/abs/1304.4550
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