Phase diagram of superconductivity and antiferromagnetism in single crystals of Sr(Fe 1 − x Co x ) 2 As 2 and Sr 1 − y Eu y (Fe 0 . 88 Co 0 . 12 ) 2 As 2
Year: 2011
Type: article
Abstract: We report magnetic susceptibility, resistivity, and heat capacity measurements on single crystals of the Sr(Fe${}_{1\ensuremath{-}x}$Co${}_{x}$)${}_{2}$As${}_{2}$ and Sr${}_{1\ensuremath{-}y}$Eu${}_{y}$(Fe${}_{0.88}$Co${}_{0.12}$)${}_{2}$As${}_{2}$ series. The optimal Co concentration for superconductivity in Sr(Fe${}_{1\ensuremath{-}x}$Co${}_{x}$)${}_{2}$As${}_{2}$ is determined to be $x~0.12$. On the basis of this, we grew members of the Sr${}_{1\ensuremath{-}y}$Eu${}_{y}$(Fe${}_{0.88}$Co${}_{0.12}$)${}_{2}$As${}_{2}$ 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 Eu${}^{2+}$ doping and coexists with antiferromagnetic ordering of Eu${}^{2+}$ as long as ${T}_{c}>{T}_{N}$. For $y\ensuremath{\geqslant}0.65$, ${T}_{N}$ crosses ${T}_{c}$ 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 Eu${}^{2+}$ sublattice destroys bulk superconductivity when ${T}_{N}>{T}_{c}$.
Source: Physical Review B
Institutions: Iowa State University, Ames National Laboratory
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Awards: G249831736, G6620285704
OpenAlex ID: W2103474565