Anisotropy of Ca0.73La0.27(Fe0.96Co0.04)As(2)studied by torque magnetometry

Abstract

Torque measurements were performed on single crystal samples of Ca0.73La0.27(Fe0.96Co0.04)As(2)in both the normal and superconducting states. Contributions to the torque signal from the paramagnetism and the vortex lattice were identified. The superconducting anisotropy parameter gamma was determined from the reversible part of the vortex contribution based on Kogan's model. It is found that gamma similar or equal to 7.5 att=T/T-c= 0.85, which is smaller than the result of CaFe0.88Co0.12AsF gamma similar or equal to 15 att= 0.83, but larger than the result of 11 and 122 families, where gamma stays in the range of 2-3. The moderate anisotropy of this 112 iron-based superconductor fills the gap between 11, 122 families and 1111 families. In addition, we found that the gamma shows a temperature dependent behavior, i.e., decreasing with increasing temperature. The fact that gamma is not a constant point towards a multiband scenario in this compound.