American Physical Society, Physical review B, 2(80)
DOI: 10.1103/physrevb.80.024508
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By muon spin-relaxation measurements on single-crystal specimens, we show that superconductivity in the $A{\text{Fe}}_{2}{\text{As}}_{2}$ $(A=\text{Ca},\text{Ba},\text{Sr})$ systems, in both the cases of composition and pressure tunings, coexists with a strong static magnetic order in a partial volume fraction. The superfluid response from the remaining paramagnetic volume fraction of $({\text{Ba}}_{0.5}{\text{K}}_{0.5}){\text{Fe}}_{2}{\text{As}}_{2}$ exhibits a nearly linear variation in $T$ at low temperatures, suggesting an anisotropic energy gap with line nodes and/or multigap effects.