Anisotropic Superconductivity and Magnetism in RbEuFe<sub>4</sub>As<sub>4</sub>
ORAL
Abstract
RbEuFe4As4 is a stoichiometric compound that undergoes a superconducting transition at Tc = 37 K and a magnetic transition at Tn = 15 K in which Eu-moments order into a type–A antiferromagnetic structure. Thus, an interleaved stacking of ferromagnetic Eu-layers and superconducting Fe2As2 layers arises. Using magnetoresistance, magnetization and specific heat measurements we construct the magnetic and superconducting phase diagrams and find that the anisotropy Γ of the upper critical field Hc2 is surprisingly low, Γ ~ 1.8. No re-emergent resistive state associated with the onset of magnetic order is seen below Tc for current flow in or out of plane. The saturation field for the Eu-moments is ~2 kG for in-plane fields and ~20 kG for out-of-plane magnetization, consistent with an in-plane moment orientation. Specific heat measurements reveal that in magnetic fields, magnetic fluctuations become pronounced extending to temperatures well above Tc. We attribute a negative normal-state magnetoresistance for in-plane as well as c-axis currents to scattering by these magnetic fluctuations.
*This work was supported by the U.S. DoE-BES, KW acknowledges support through an Early Postdoc Mobility Fellowship of the Swiss National Science Foundation.
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Presenters
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Ulrich Welp
- Materials Science Division, Argonne National laboratory
- Argonne Natl Lab
- Argonne National Laboratory
- Materials Science Division, Argonne National Laboratory
- Material Science Division, Argonne National Laboratory