Anisotropic physical properties and large critical current density in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">K</mml:mi><mml:msub><mml:mi>Ca</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Fe</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">F</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> single crystal
Sunseng Pyon, Yuto Kobayashi, Ayumu Takahashi, Wenjie Li, Teng Wang, Gang Mu, Ataru Ichinose, Tadashi Kambara, Atsushi Yoshida, Tsuyoshi Tamegai
Abstract
We present a systematic study of electrical resistivity, Hall coefficient, magneto-optical imaging, magnetization, and scanning transmission electron microscopy (STEM) analyses of $\mathrm{K}{\mathrm{Ca}}_{2}{\mathrm{Fe}}_{4}{\mathrm{As}}_{4}{\mathrm{F}}_{2}$ 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 ${\ensuremath{\rho}}_{c}/{\ensuremath{\rho}}_{ab}>100$, and semiconductorlike ${\ensuremath{\rho}}_{c}$ suggest that the electronic state is quasi-two-dimensional. Hall effect measurements indicate that $\mathrm{K}{\mathrm{Ca}}_{2}{\mathrm{Fe}}_{4}{\mathrm{As}}_{4}{\mathrm{F}}_{2}$ is a multiband system with holes as main carriers. Magnetization measurements reveal significantly larger ${J}_{\mathrm{c}}$ compared with that in other iron-based superconductors with different values of ${J}_{\mathrm{c}}$ depending on the direction of magnetic field. The origin of these ${J}_{\mathrm{c}}$ characteristics is discussed based on microstructural observations using STEM. In addition, further enhancement of ${J}_{\mathrm{c}}$ in $\mathrm{K}{\mathrm{Ca}}_{2}{\mathrm{Fe}}_{4}{\mathrm{As}}_{4}{\mathrm{F}}_{2}$ for future high-field application is demonstrated in terms of heavy-ion irradiation.