Angular dependent studies of vortex pinning and dynamics in RbEuFe<sub>4</sub>As<sub>4</sub> single crystals with columnar defects
ORAL
Abstract
We performed studies of vortex pinning and dynamics in RbEuFe4As4 single crystals with different densities and orientations of aligned columnar defects (CDs) introduced by heavy ion irradiation, as a function of temperature (T) and magnetic field strength (H) and orientation (Θ). Pristine crystals have a superconducting transition temperature Tc~37K and a magnetic ordering transition of the Eu at Tm~15K, neither of which is changed by the irradiations. We developed a model to account for the modifications to the vortex critical state produced by the magnetic moments. Irradiated crystals exhibit large critical current densities (Jc) and a lock-in phase (where vortices remain fully trapped into the CDs even if H is tilted away from them), which is the fingerprint of correlated pinning. For large CDs densities (e.g. matching field BΦ ~ 10T) the lock-in phase spans an unusually large angular range and extends to fields above 2T. This allows us to investigate the angular variations of Jc and the creep rates associated with the expansion of half-loops and double-kinks inside the lock-in region, due to the changes in the pinning energy arising from the –B●H/4π term in the free energy.
*Work funded by US DOE, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.
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Presenters
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Ivan Nekrashevich
- Los Alamos National Laboratory
- Los Alamos Natl Lab