Upper critical fields and superconducting anisotropy of K_0.70Fe_1.55Se_1.01S_0.99 and K_0.76Fe_1.61Se_0.96S_1.04 single crystals

Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory Upton, NY 11973, USA

^a petrovic@bnl.gov

Received: 14 May 2011
Accepted: 19 July 2011

Abstract

We have investigated temperature and angular dependence of resistivity of K_0.70(7)Fe_1.55(7)Se_1.01(2)S_0.99(2) and K_0.76(5)Fe_1.61(5)Se_0.96(4)S_1.04(5) single crystals. The upper critical fields μ₀H_c2(T) for both field directions decrease with the increase in S content. On the other hand, the angle-dependent magnetoresistivity for both compounds can be scaled onto one curve using the anisotropic Ginzburg-Landau theory. The obtained anisotropy of μ₀H_c2(T) increases with S content, implying that S doping might decrease the dimensionality of certain Fermi surface parts, leading to stronger two-dimensional character.