Vortex Dynamics and Pinning in CaKFe4As4 Single Crystals from DC Magnetization Relaxation and AC Susceptibility

• Published in: Condensed matter Vol. 8; no. 4; p. 93
• Main Authors: Ionescu, Alina M., Ivan, Ion, Miclea, Corneliu F., Crisan, Daniel N., Galluzzi, Armando, Polichetti, Massimiliano, Crisan, Adrian
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-12-2023
• Subjects: Anisotropy; CaKFe4As4 single crystals; Cooling; Critical current density; Critical field (superconductivity); Critical temperature; elastic creep to plastic creep crossover; Electrons; Fe-based superconductors; frequency-dependent AC susceptibility; Hysteresis loops; Liquid hydrogen; Magnetic fields; Magnetic induction; magnetic relaxation; Magnetization; pinning potential; Single crystals; Superconductors; Temperature; Temperature dependence; Vortices
• ISSN: 2410-3896; 2410-3896
• DOI: 10.3390/condmat8040093

Among various “families” of iron-based superconductors, the quite recently discovered AeAFe4As4 (where Ae is an alkali-earth metal and A is an alkali metal) has high critical current density, a very high upper critical field, and a low anisotropy, and has recently received much interest for the possibility of high magnetic field applications at the liquid hydrogen temperature. We have performed DC magnetization relaxation and frequency-dependent AC susceptibility measurements on high-quality single crystals of CaKFe4As4 with the aim of determining the pinning potential U*. The temperature dependence of U* displays a clear crossover between elastic creep and plastic creep. At temperatures around 27–28 K, U* has a very high value, up to 1200 K, resulting in an infinitesimally small probability of thermally activated flux jumps. From the dependence of the normalized pinning potential on irreversible magnetization, we have determined the creep exponents in the two creep regimes, which are in complete agreement with theoretical models. The estimation of the pinning potential from multifrequency AC susceptibility measurements was possible only near the critical temperature due to equipment limitations, and the resulting value is very close to the one that resulted from the magnetization relaxation data. Magnetic hysteresis loops revealed a second magnetization peak and very high values of the critical current density.