  The 55Mn nuclear magnetic resonance spectrum of noncollinear 12-sublattice
antiferromagnet Mn3Al2Ge3O12 has been studied in the frequency range of 200 -
640 MHz in the external magnetic field H || [001]} at T=1.2 K. Three absorption
lines have been observed in fields less than the field of the reorientation
transition Hc at the polarization h||H of the rf field. Two lines have been
observed at H > Hc and h_|_H. The spectral parameters indicate that the
magnetic structure of manganese garnet differs slightly from the exchange
triangular 120-degree structure. The anisotropy of the spin reduction and (or)
weak antiferromagnetism that are allowed by the crystal symmetry lead to the
difference of approximately 3% in the magnetization of sublattices in the field
H < Hc. When the spin plane rotates from the orientation perpendicular to the
C3 axis to the orientation perpendicular to the C4 axis, all magnetic moments
of the electronic subsystem decrease by approximately 2% from the average value
in the zero field.
