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STSM of Alina Ionescu at MPI-IS (Germany): Vortex dynamics and pinning in HTS/FM heterostructures

The purpose of the STSM was to study at Max Planck Institute (MPI) for Intelligent Systems, department of Modern Magnetic Systems, Stuttgart, Germany, vortex dynamics and pinning in heterostructures of YBa2Cu3O7 (YBCO) with magnetic CaRuO3 (CRO) and YBCO with CaRuO3 separated by a thin layer of 5nm SrTiO3 (STO). Determination of basic superconducting properties (critical temperature, irreversibility field, critical current density), investigation of pinning force and of magnetic relaxation at long time scales led to fundamental research on the vortex diagram, the vortex melting line and pinning in HTS thin films.  The materials were better characterized over a wide range of temperatures (10-300 K) and magnetic fields (up to 7 T). Measurements above Tc of YBCO were made to see the behaviour of the ferromagnet.

The deposition of a ferromagnetic layer can affect the properties of high-temperature superconductors underneath. The influence of ferromagnetic CaRuO3 on the properties of YBCO superconducting thin films was investigated. The studied samples were two reference samples (YBCO and YBCO/STO), YBCO/CRO and YBCO/STO/CRO and the last two were post oxygenated (YBCO/CRO oxy and YBCO/STO/CRO oxy). Magnetometry and relaxation measurements showed that the modification of the superconducting properties of YBCO strongly depends on the interaction with the ferromagnetic layer on top. The barrier layer has a great impact on both the superconducting properties of the YBCO film and the ferromagnetic ordering of CaRuO3. The results were presented in Ionescu A M et al, Materials 2022, 15, 2345. During the STSM several fruitful meetings took place to discuss future collaborations and joint projects.

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