Anisotropy in Superconducting CsCa₂Fe₄As₄F₂ Single Crystals

CsCa₂Fe₄As₄F₂ is a typical example of 12442-type iron-based superconductors. The novel material superconducts at 29.5 K without extrinsic chemical doping. It contains double Fe₂As₂ layers that are separated by insulating Ca₂F₂ layers. The structural feature may lead to the weak interlayer coupling and strong anisotropy. In this work we successfully synthesized high quality CsCa₂Fe₄As₄F₂ single crystals with CsAs flux. Measurements of X-ray diffraction, anisotropic magnetotransport and magnetization were carried out to characterize the single crystals. The anisotropic superconducting upper H_c2 (T), lower critical field H_c1 (T), the anisotropy parameter γ (T) and other related parameters were obtained. The results indicate that CsCa₂Fe₄As₄F₂ is one of most anisotropic iron-based superconductors.