Nuclear magnetic resonance in noncollinear antiferromagnet Mn3Al2Ge3O12

The Mn-55 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 aEuro- [001] at T = 1.2 K. Three absorption lines have been observed in fields less than the field of the reorientation transition H (c) at the polarization h aEuro- H of the rf field. Two lines have been observed at H > H (c) and h aSyen 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 a parts per thousand 3% in the magnetization of sublattices in the field H < H (c). When the spin plane rotates from the orientation perpendicular to the C (3) axis to the orientation perpendicular to the C (4) axis, all magnetic moments of the electronic subsystem decrease by a parts per thousand 2% from the average value in the zero field.