  In the present study, we investigated magnetodielectric, magnetoelectric
(ME), and angular-dependent polarization in single-crystal Fe4Nb2O9. The
magnetodielectric effects in epsilon(x) (x//[100]), epsilon(y) (y//[120]), and
epsilon(z) (z//[001]) are found to be significant only around T-N approximate
to 95 K when magnetic fields are applied along three orthogonal x-, y-
(y//[120]), and z directions. The finite polarization P-x, P-y, and P-z of 70,
100, and 30 mu C/m(2), respectively, can be induced in the antiferromagnetic
phase when a finite magnetic field up to 9 T is applied along the three
orthogonal directions. The angular-dependent polarization measurements verify
the dominating linear ME effects below T-N. From the above experimental
results, a linear ME tensor a(ij) with all nine nonzero components can be
inferred, demonstrating a much lower magnetic point group of -1' for the canted
antiferromagnetic configuration.
