Nuclear Magnetic Resonance in Noncollinear Antiferromagnet Mn3Al2Ge3O12

TL;DR

This study investigates the 55Mn nuclear magnetic resonance spectrum of the noncollinear antiferromagnet Mn3Al2Ge3O12 at low temperature, revealing details about its magnetic structure and spin dynamics under varying magnetic fields.

Contribution

The paper provides new insights into the magnetic structure and spin behavior of Mn3Al2Ge3O12 using NMR spectroscopy, highlighting slight deviations from the ideal exchange triangular structure.

Findings

Identification of three absorption lines below the reorientation transition field

Observation of two lines above the transition field

Detection of a ~3% difference in sublattice magnetizations and ~2% decrease in magnetic moments during spin plane rotation

Abstract

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.