Site Split of Antiferromagnetic alpha-Mn Revealed by 55Mn Nuclear Magnetic Resonance

The magnetic structure of antiferromagnetic alpha-Mn has been unclarified for almost 70 years since its magnetism was discovered. We measured the zero -field nuclear magnetic resonance spectra of antiferromagnetic alpha-Mn to obtain further insight into magnetism below TN = 95 K. The site II spectra split into two sites with five subpeaks owing to quadrupole interaction, and this shows that the ordered moments at site II are slightly tilted from the [001] direction. The site III spectra revealed that this site splits into four sites below TN. These findings clearly demonstrate that the antiferromagnetic alpha-Mn symmetry is lower than previously considered.