Site Split of Antiferromagnetic $\alpha$-Mn Revealed by $^{55}$Mn Nuclear Magnetic Resonance

TL;DR

This study uses $^{55}$Mn NMR to clarify the magnetic structure of antiferromagnetic $ ext{α}$-Mn, revealing complex site splitting and lower symmetry than previously thought.

Contribution

It provides the first detailed NMR analysis showing site splitting and symmetry reduction in $ ext{α}$-Mn's antiferromagnetic state.

Findings

Site II splits into two sites with five subpeaks.

Site III splits into four sites below $T_N$.

Ordered moments at site II are slightly tilted.

Abstract

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 $T_{\text{N}} = 95$ 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 $T_{\text{N}}$. These findings clearly demonstrate that the antiferromagnetic $\alpha$-Mn symmetry is lower than previously considered.