  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 ({\epsilon}')
vs T and loss (tan{\delta}) vs T at different temperatures, i.e. 12.5, 30, 50
and 58K; at low temperatures, three magnetic-field-induced transitions are
observed in {\epsilon}' vs H at 6, 40 and 60 kOe. These transition temperatures
and critical magnetic fields track those obtained from magnetization data. This
establishes the existence of strong magnetoelectric coupling in this compound.
(ii) Correspondingly, electric polarization could be observed as a function of
T and H in the magnetically ordered state, thereby indicating magnetism-induced
ferroelectricity in this compound; this result suggests that this compound is a
possible new multiferroic material among spin = 1 (nickel containing) compounds
with successive magnetic transitions and strong magnetoelectric coupling.
