Figure 1

(Color online) (a) Temperature dependence of the in-plane penetration depth of three different single crystals of ${\text{SmFeAsO}}_{0.8}{\text{F}}_{0.2}$. The solid lines are fits to Eq. (1). Data below $T=3.2\text{K}$ were excluded from the fits. The data sets for samples 1 and 2 are offset for clarity. The inset shows the data for sample 3 (above 3.2 K only) corrected for paramagnetic normal-state contributions, assuming the magnetic moment values listed. The solid lines are fits to a power-law dependence $\Delta \lambda \propto T^n$. (b) Oscillator frequency shift (proportional to changes in the in-plane penetration depth) for a powder sample. The inset expands the low $T$ portion of the plot. (c) Susceptibility close to $T_c$ for the three single-crystal samples and (d) for the powder (solid symbols) and sintered pellet (open symbols).Reuse & Permissions

Figure 2

(Color online) Calculated normalized superfluid density $\left[{\lambda }^2\left(0\right)/{\lambda }^2\left(T\right)\right]$ versus temperature for sample 3 using different assumed values for the zero-temperature penetration depth $\lambda \left(0\right)$. The solid lines are fits to the two-gap model described in the text, and the inset table shows the fit parameters. The dashed line shows the isotropic $s$-wave BCS prediction with ${\Delta }_0=1.76k_B{T}_c$. Note that for clarity not all data points are plotted. The inset shows the low-temperature data on an expanded scale.Reuse & Permissions