Millimeter sized single crystals of KCa_2Fe_4As_4F_2 were grown using a self-flux method. The chemical compositions and crystal structure were characterized carefully. Superconductivity with the critical transition T_c = 33.5 K was confirmed by both the resistivity and magnetic susceptibility measurements. Moreover, the upper critical field H_c2 was studied by the resistivity measurements under different magnetic fields. A rather steep increase for the in-plane H_c2^ab with cooling, d\mu_0H_c2^a/dT|T_c = -50.9 T/K, was observed, indicating an extremely high upper critical field. Possible origins for this behavior were discussed. The findings in our work is a great promotion both for understanding the physical properties and applications of 12442-type Fe-based superconductors.
@article{arxiv.1903.04822,
title = {Single-crystal growth and extremely high H_c2 of 12442-type Fe-based superconductor KCa_2Fe_4As_4F_2},
author = {Teng Wang and Jianan Chu and Hua Jin and Jiaxin Feng and Lingling Wang and Yekai Song and Chi Zhang and Wei Li and Zhuojun Li and Tao Hu and Da Jiang and Wei Peng and Xiaosong Liu and Gang Mu},
journal= {arXiv preprint arXiv:1903.04822},
year = {2019}
}