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arXiv · 2601.20281

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

Yusuke Sakai·Fumiya Hori·Hiroki Matsumura·Shumpei Oguchi·Shunsaku Kitagawa·Kenji Ishida·Hiroshi Tanida
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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.

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Yusuke Sakai, Fumiya Hori, Hiroki Matsumura, Shumpei Oguchi, Shunsaku Kitagawa, Kenji Ishida, Hiroshi Tanida. 2026-01-28. Microscopic Determination of the c-axis-Oriented Antiferromagnetic Structure in LaMnSi by $^{55}$Mn and $^{139}$La NMR. https://doi.org/10.7566/jpsj.95.024702

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