  We report that the spin-chain compound Dy2BaNiO5 recently proven to exhibit
magnetoelectric coupling below its Neel temperature (T_N) of 58 K, exhibits
strong frequency-dependent behavior in ac magnetic susceptibility and complex
dielectric properties at low temperatures (<10K), mimicking 'reentrant'
multiglass phenomenon. Such a behavior is not known among undoped compounds. A
new finding in the field of multiferroics is that the characteristic magnetic
feature at such low temperatures moves towards higher temperatures in the
presence of a magnetic-field (H), whereas the corresponding dielectric feature
shifts towards lower temperatures with H, unlike the situation near T_N. This
observation indicates that the alignment of spins by external magnetic fields
tends to inhibit glassy-like slow electric-dipole dynamics, at least in this
system, possibly arising from peculiarities in the magnetic structure.
