$^{19}$F NMR and defect spins in vacuum-annealed LaO$_{0.5}$F$_{0.5}$BiS$_2$
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| Auteurs principaux: | , , , , , , , , , , , |
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| Format: | Preprint |
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2024
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| author | Yadav, S. Delgado, S. Bernal, O. O. MacLaughlin, D. E. Liu, Y. Jiang, D. Santana, O. Mushammel, A. Shu, Lei Huang, K. Yazici, D. Maple, M. B. |
| author_facet | Yadav, S. Delgado, S. Bernal, O. O. MacLaughlin, D. E. Liu, Y. Jiang, D. Santana, O. Mushammel, A. Shu, Lei Huang, K. Yazici, D. Maple, M. B. |
| contents | We report results of magnetization and $^{19}$F NMR measurements in the normal state of as-grown LaO$_{0.5}$F$_{0.5}$BiS$_2$. The magnetization is dominated by a temperature-independent diamagnetic component and a field- and temperature-dependent paramagnetic contribution $M_μ(H,T)$ from a $\sim$1000~ppm concentration of local moments, an order of magnitude higher than can be accounted for by measured rare-earth impurity concentrations. $M_μ(H,T)$ can be fit by the Brillouin function $B_J(x)$ or, perhaps more realistically, a two-level $\tanh(x)$ model for magnetic Bi $6p$ ions in defect crystal fields. Both fits require a phenomenological Curie-Weiss argument $x = μ_\mathrm{eff}H/(T + T_W)$, $T_W \approx 1.7$ K. There is no evidence for magnetic order down to 2 K, and the origin of $T_W$ is not clear. $^{19}$F frequency shifts, linewidths, and spin-lattice relaxation rates are consistent with purely dipolar $^{19}$F/defect-spin interactions. The defect-spin correlation time $τ_c(T)$ obtained from $^{19}$F spin-lattice relaxation rates obeys the Korringa relation $τ_cT = \text{const.}$, indicating the relaxation is dominated by conduction-band fluctuations. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2408_06284 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | $^{19}$F NMR and defect spins in vacuum-annealed LaO$_{0.5}$F$_{0.5}$BiS$_2$ Yadav, S. Delgado, S. Bernal, O. O. MacLaughlin, D. E. Liu, Y. Jiang, D. Santana, O. Mushammel, A. Shu, Lei Huang, K. Yazici, D. Maple, M. B. Strongly Correlated Electrons Materials Science Superconductivity We report results of magnetization and $^{19}$F NMR measurements in the normal state of as-grown LaO$_{0.5}$F$_{0.5}$BiS$_2$. The magnetization is dominated by a temperature-independent diamagnetic component and a field- and temperature-dependent paramagnetic contribution $M_μ(H,T)$ from a $\sim$1000~ppm concentration of local moments, an order of magnitude higher than can be accounted for by measured rare-earth impurity concentrations. $M_μ(H,T)$ can be fit by the Brillouin function $B_J(x)$ or, perhaps more realistically, a two-level $\tanh(x)$ model for magnetic Bi $6p$ ions in defect crystal fields. Both fits require a phenomenological Curie-Weiss argument $x = μ_\mathrm{eff}H/(T + T_W)$, $T_W \approx 1.7$ K. There is no evidence for magnetic order down to 2 K, and the origin of $T_W$ is not clear. $^{19}$F frequency shifts, linewidths, and spin-lattice relaxation rates are consistent with purely dipolar $^{19}$F/defect-spin interactions. The defect-spin correlation time $τ_c(T)$ obtained from $^{19}$F spin-lattice relaxation rates obeys the Korringa relation $τ_cT = \text{const.}$, indicating the relaxation is dominated by conduction-band fluctuations. |
| title | $^{19}$F NMR and defect spins in vacuum-annealed LaO$_{0.5}$F$_{0.5}$BiS$_2$ |
| topic | Strongly Correlated Electrons Materials Science Superconductivity |
| url | https://arxiv.org/abs/2408.06284 |