# Anisotropic up to 92 T and the signature of multiband superconductivity in Ca (Pt As )((Fe Pt ) As )

## Author(s): Mun, Eundeok; Ni, Ni; Allred, Jared M.; Cava, Robert J.; Ayala, Oscar; et al

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 Abstract: The upper critical fields H c2(T) of single crystals of the superconductor Ca 10(Pt 4-δAs 8)((Fe 0.97Pt 0.03) 2As 2) 5 (δ0.246) are determined over a wide range of temperatures down to T=1.42 K and magnetic fields of up to μ 0H92 T. The measurements of anisotropic H c2(T) curves are performed in pulsed magnetic fields using radio-frequency contactless penetration depth measurements for magnetic field applied both parallel and perpendicular to the ab plane. Whereas a clear upward curvature in Hc2(T) along Hc is observed with decreasing temperature, the Hc2ab(T) along Hab shows a flattening at low temperatures. The rapid increase of the Hc2c(T) at low temperatures suggests that the superconductivity can be described by two dominating bands. The anisotropy parameter γ HHc2ab/Hc2c is ∼7 close to T c and decreases considerably to ∼1 with decreasing temperature, showing rather weak anisotropy at low temperatures. © 2012 American Physical Society. Publication Date: Mar-2012 Electronic Publication Date: 5-Mar-2012 Citation: Mun, Eundeok, Ni, Ni, Allred, Jared M., Cava, Robert J., Ayala, Oscar, McDonald, Ross D., Harrison, Neil, Zapf, Vivien S. (2012). Anisotropic up to 92 T and the signature of multiband superconductivity in Ca (Pt As )((Fe Pt ) As ). Physical Review B, 85 (10), 10.1103/PhysRevB.85.100502 DOI: doi:10.1103/PhysRevB.85.100502 ISSN: 1098-0121 EISSN: 1550-235X Pages: 85.10:100502-1- 100502-4 Type of Material: Journal Article Journal/Proceeding Title: Physical Review B Version: Final published version. This is an open access article. Notes: Physical Review B - Condensed Matter and Materials Physics. Volume 85, Issue 10, 5 March 2012, Article number 100502.