Figure 1

(Color online) Magnetic susceptibility $\chi \left(T\right)$ measured at $H=0.1\text{T}$ of SC ${\text{BaFe}}_2{\text{As}}_2$. A small anomaly at 85 K (arrow) is clearly visible. Inset: resistivity and specific heat versus temperature in the SC sample.Reuse & Permissions

Figure 2

(Color online) (a) Full ${}^{75}\text{A}\text{s}$ NMR spectra at a fixed frequency of 45 MHz and at 120 K. The satellite peaks (blue lines for $H\perp c$ and red lines for $H\parallel c$) are equally spaced. For simplicity, we omit the central line for $H\perp c$ which is 0.1 kG off from the central line for $H\parallel c$. (b) Central lines for both $H\perp c$ and $H\parallel c$. The vertical dotted lines represent the midpoint between the satellites. (c) Comparison of spectra in the SC sample for two different fields $\left(H\perp c\right)$ at 220 K. (d) The Knight shift of the primary (red, blue) site and the secondary site (gray) versus temperature. The solid (open) gray triangles correspond to $H\perp c$ $\left(H\parallel c\right)$ and the vertical green line at 85 K corresponds to $T_N$.Reuse & Permissions

Figure 3

(Color online) ${}^{75}\text{A}\text{s}$ NMR spectra of the central transition in ${\text{BaFe}}_2{\text{As}}_2$ for both the SC and PC samples at 45 MHz for the case of (a) $H\perp c$ at 6.139 T, (b) $H\parallel c$ at 6.149 T, and (c) the polycrystal sample at $H=6.148\text{T}$. Two peaks are clearly distinguished in the SC. Below the ordering transition, the spectra quickly broaden and the signal is drastically reduced.Reuse & Permissions

Figure 4

(Color online) (a) $T_1^{-1}$ versus $T$ in ${\text{BaFe}}_2{\text{As}}_2$ at 45 MHz for field along $c$ and in the $ab$ plane. The dotted red line at 85 K indicates the second-order transition (disordered sample) and the solid green line at 138 K indicates the first-order transition (pure sample). An additional weak maximum at 150 K is evident only for $H\perp c$. The solid lines are guides for the eyes. (b) ${\left(T_{1}T\right)}^{-1}$ versus $T$. The dotted curves are fits as described in the text, and the gray data points are reproduced from Ref. 18.Reuse & Permissions