Probing superconducting anisotropy of single crystal KCa2Fe4As4F2 by magnetic torque measurements

Abstract

Anisotropy is the key to understanding iron-based superconductors, which usually have quasi-two-dimensional layered structures. By using torque measurements (a sensitive tool to detect the magnetic anisotropy), we investigate the superconducting anisotropy of the KCa2Fe4As4F2 (12442, Tc=33K) single crystal. In the normal state, the torque data display a paramagnetic behavior H2sin2θ in different applied magnetic fields H aligned at an angle θ to the c axis of the crystal, while in the mixed state vortex torque dominates the torque signal. The anisotropy parameter γ and London penetration depth λ were obtained from vortex torque analyzed using Kogan's formula. It was found that γ is 16.2 at T=25K (≈0.76 Tc), close to γ≈ 15 at T ≈ 0.76 Tc for CaFe0.88Co0.12AsF, but much larger than the result of 11 and 122 families, where γ is around 3. In addition, the obtained perpetration depth from the torque measurements is consistent with the results of μSR measurements of KCa2Fe4As4F2. Our results suggest that the two-dimensionality plays a vital role in the superconductivity of the 12442-type iron-based superconductor.

Source-reported materials — not catalogue approval

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