Electron correlations and charge segregation in layered manganese pnictide antiferromagnets showing anomalously large magnetoresistance

A family of layered manganese-pnictide antiferromagnets BaMn(2)Pn(2) (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 Mn-55 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 Mn-55 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 Mn-55 spin-lattice relaxation. The characteristic temperatures of the appearance of these additional features in the magnetic response probed by Mn-55 NMR correlate well with the anomalies in the resistivity and anomalously large MR, which hints that the two phenomena are connected.

Automated summary

Recent research on layered manganese-pnictide antiferromagnets BaMn(2)Pn(2) (Pn=P, As, Sb, Bi) has shown anomalously large magnetoresistance, with underlying factors such as weakly localized charge carriers and collective spin fluctuations potentially affecting the phenomenon. The study used local-probe Mn-55 nuclear magnetic resonance (NMR) to investigate the microscopic picture of magnetoresistance and found correlations between the appearance of additional features in the magnetic response, resistivity anomalies, and anomalously large MR, suggesting a connection between these phenomena.