  By means of magnetic susceptibility and specific heat measurements, x-ray and
unpolarised neutron diffraction investigations on powder and single-crystal
samples, simultaneous long-range antiferromagnetic Fe and Nd ordering in
NdFe3(11BO3)4 with R 3 2 chemical structure has been found at temperatures
below TN = 30.5(5) K down to 1.6 K. At temperatures down to 20 K to the
propagation vector is khex = [0,0,3/2] and becomes slightly incommensurate at
lower temperatures. Symmetry analysis yields magnetic spiral configurations
with the magnetic moments oriented parallel to hexagonal basal plane according
to the irreducible representations tau_3 in the commensurate case. This is in
agreement with the easy directions of magnetisation perpendicular to the c-axis
as determined by magnetic susceptibility measurements. At 1.6 K the magnetic Fe
moment amounts to 4.9 muB close to the free ion moment of Fe3+. The magnetic
Nd3+ moment saturates presumably due to crystal-field effects at 2.7 muB.
