Research objectives and content
Many novel vortex phases present in the field -temperature phase diagram of High-T, superconductors. A novel vortex phase name Bragg glass with properties between a glass and a perfect lattice is expected to thermally melt to a flux liquid via afrst order melting transition. Recent latent heat measurements suggest that the defects in the samples drive the melting transition from Ist to 2nd. One then expects two bicritical points in a given sample that should be observable only at low defect densities. We plan to perform micro-calorimetry experiments (resolution: 10/9Joule/K) in the field range 0-30 Tesla in order to trace for thefirst time the latent heat and entropy of these phase transitions. We also plan to perform l-V measurements on single crystal rings with subpicoVolt resolution in order to check predictions of vortex glass theory in ordered samples. We intend to combine the above results with measurements of the magneto-caloric effect, a utlique trace of phase transitions at low fields. We expect to trace the latent heat of flux lattice melting and find the first thermodynamic proof that the vortex glass-vortex liquid is a true phase transition. We also expect a possible evidence for a Bragg glass-vortex glass transition and a possible evidence for re-entrant flux lattice melting at low magnetic inductions.
Training content (objective, benefit and expected impact)
The vortex phase diagram is a cutting edge problem rapidly advancing. This project. supported by advanced technological tools, will answer some key questions and also influence manvoer fields such as polymorphs and generally disordered matter physics. Training will be received in advanced technologic areas such as micro-magnetic sensor-b-thermal sensors, integrated suspended membranes techniques and focused LASER ablation and will be a certificate for an academic and industrial carreer. Links with industry / industrial relevance (22)
Vortex behavior will shape scientifically su-e(ce=d- and commercially its potential applications. This project will be a field of common interest with SCHNEIDER ELECTRIC SA France on the problem of high critical currents and its relation with twin planes and defects. The micro-magnetic sensors part of the project will be realized in collaboration with IXTREM SA. France, specialized on industrial applications of magnetic and electriomagnetic technologies. The part concerning LASER beam patterning will be realized in collaboration with IBM Yorktwon Heights, New York, USA.