  We have grown single crystals of multiferroic double-perovskite Lu2CoMnO6 and
studied the directional dependence of their magnetic and dielectric properties.
The ferromagnetic order emerges below TC ~ 48K along the crystallographic c
axis. Dielectric anomaly arises along the b axis at TC, contrary to the
polycrystalline work suggesting ferroelectricity along the c axis. Through the
strongly coupled ferromagnetic and dielectric states, the highly non-linear
variation of both dielectric constant and magnetization was achieved in
application of magnetic fields. This concurrent tunability provides an
efficient route to manipulation of multiple order parameters in multiferroics.
