Journal or Book Title
Physical Review B
We report magnetic susceptibility, resistivity, and heat capacity measurements on single crystals of the Sr(Fe1−xCox)2As2 and Sr1−yEuy(Fe0.88Co0.12)2As2 series. The optimal Co concentration for superconductivity in Sr(Fe1−xCox)2As2 is determined to be x~0.12. On the basis of this, we grew members of the Sr1−yEuy(Fe0.88Co0.12)2As2 series so as to examine the effects of well-defined, local magnetic moments on the superconducting state. We show that superconductivity is gradually suppressed by paramagnetic Eu2+ doping and coexists with antiferromagnetic ordering of Eu2+ as long as Tc>TN. For y⩾0.65, TN crosses Tc and the superconducting ground state (as manifested by zero resistivity) abruptly disappears with evidence for competition between superconductivity and local moment antiferromagnetism for y up to 0.72. It is speculated that the suppression of the antiferromagnetic fluctuations of the Fe sublattice by coupling to the long-range order of the Eu2+ sublattice destroys bulk superconductivity when TN>Tc.
American Physical Society
Hu, Rongwei; Bud'ko, Sergey L.; Straszheim, Warren E.; and Canfield, Paul C., "Phase diagram of superconductivity and antiferromagnetism in single crystals of Sr(Fe1−xCox)2As2 and Sr1−yEuy(Fe0.88Co0.12)2As2" (2011). Ames Laboratory Publications. 200.