Anisotropic physical properties and large critical current density in KCa2Fe4As4F2 single crystal
Abstract
We present a systematic study of electrical resistivity, Hall coefficient, magneto-optical imaging, magnetization, and STEM analyses of KCa2Fe4As4F2 single crystals. Sharp diamagnetic transition and magneto-optical imaging reveal homogeneity of single crystal and prominent Bean-like penetrations of vortices. Large anisotropy of electrical resistivity, with c / ab > 100, and semiconductor-like c suggest that the electronic state is quasi two-dimensional. Hall effect measurements indicate that KCa2Fe4As4F2 is a multiband system with holes as main carriers. Magnetization measurements reveal significantly larger Jc compared with that in other iron-based superconductors with different values of Jc depending on the direction of magnetic field. Origin of these Jc characteristics is discussed based on microstructural observations using STEM. In addition, further enhancement of Jc in KCa2Fe4As4F2 for future application is demonstrated in terms of heavy-ion irradiation.