Microscopic Determination of the c-axis-Oriented Antiferromagnetic Structure in LaMnSi by $^{55}$Mn and $^{139}$La NMR

TL;DR

This study uses NMR techniques to reveal the antiferromagnetic structure and electronic properties of LaMnSi, showing Mn moments aligned along the c axis and characteristics of itinerant antiferromagnetism.

Contribution

It provides a microscopic characterization of LaMnSi's magnetic structure and electronic behavior, highlighting its suitability for studying 3d electron magnetism and odd-parity multipole order.

Findings

Mn moments align along the c axis in a C-type AFM structure

Internal magnetic field at Mn site is 19.64 T at 4.2 K

exhibits metallic behavior and magnon-induced enhancement near TN

Abstract

We report a microscopic investigation of the magnetic structure and electronic properties of LaMnSi in its antiferromagnetic (AFM) state using nuclear magnetic resonance (NMR). Field-swept $^{55}$Mn- and $^{139}$La-NMR spectra, as well as zero-field 55Mn-NMR (ZFNMR) spectra, reveal that the Mn ordered moments are parallel to the tetragonal c axis, consistent with the C-type AFM structure and the realization of an odd-parity multipole order. The internal field at the Mn site is determined to be 19.64 T at 4.2 K, corresponding to a hyperfine coupling constant of Ahf = 6.0 T/uB. Nuclear spin-lattice relaxation rate 1/T1 exhibits a characteristic behavior of itinerant antiferromagnetism, showing metallic behavior at low temperatures and magnon-induced enhancement upon approaching the Neel temperature (TN = 295 K). These results show LaMnSi as an ideal compound to study 3d electron magnetism and odd-parity multipole order in the RT Si (R = rare-earth, T = transition metal) system, free of the complexities of 4f electrons.