A family of layered manganese-pnictide antiferromagnets BaMn2Pn2 (Pn stands for P, As, Sb, and Bi) has been recently shown to host anomalously large magnetoresistance (MR) with both positive and negative MR components. In search for the microscopic picture of MR in this family, we here report a local-probe Mn55 nuclear magnetic resonance (NMR) study. The zero-field NMR spectra and the temperature dependence of the spin-lattice relaxation rates are fully consistent with the proposed G-Type antiferromagnetic order. However, a close inspection of the Mn55 NMR spectra reveals a fine structure, which is due to the weakly localized charge carriers. As these carriers localize and segregate in the presence of electron correlations, they also undergo collective spin fluctuations which freeze-out at low temperatures and thus contribute to the Mn55 spin-lattice relaxation. The characteristic temperatures of the appearance of these additional features in the magnetic response probed by Mn55 NMR correlate well with the anomalies in the resistivity and anomalously large MR, which hints that the two phenomena are connected.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics