The effects of suppressing Eu magnetic order via 20% Ca doping in single crystals of the magnetically ordered superconductor RbEu1-xCaxFe4As4

Dec. 1 14:55-15:10

*Matt Smylie1,2, Ramakanta Chapai2, Hendrik Hebbeker1, Jared Dans1, Angelo Patrizi1, Jinke Bao2, Duck Young Chung2, Mercouri Kanatzidis2,3, John Singleton4, Fedor Balakirev4, Wai-Kwong Kwok2, Ulrich Welp2
Department of Physics and Astronomy, Hofstra University, USA1
Materials Science Division, Argonne National Laboratory, USA2
Department of Chemistry, Northwestern University, USA3
National High Magnetic Field Laboratory, Los Alamos National Laboratory, USA4

We investigate the effect of Ca-for-Eu doping in single crystals of the magnetic superconductor RbEuFe4As4 at 20% doping, observing a ~1.5 K suppression of the magnetic ordering temperature with no effect on Tc. Upper critical fields measured conventionally and via pulsed-field techniques are similar to the undoped compound. At low temperature below the ferromagnetic saturation field, we find evidence of a field-induced transition to a new magnetic state not seen in the x = 0 compound. Additionally, there is a pronounced effect on the superconducting critical current measured via magnetic hysteresis loops not previously observed.

Work by MPS, JD, was in part supported by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Visiting Faculty Program (VFP). Work by RC, JKB, DYC, MGK, WKK, UW was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreements No. DMR-1157490 and No. DMR-1644779, and the State of Florida, as well as the Strongly Correlated Magnets thrust of the DoE BES “Science of 100 T” program.

Keywords: Magnetic superconductor, Ferromagnetic superconductor