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Speaker: Shiv J. Singh
(University of Oxford, Oxford)
Date: October 25, 2017 (Wednesday)
Time: 16:00 hrs (4:00 pm)
Venue: Seminar Room, First Floor, School of Physical Sciences (SPS), JNU
Abstract: Iron-based superconductors have huge potential for high magnetic field applications possessing to their ultrahigh upper critical field (Hc2) and very small anisotropy. Single crystals and thin films studies have proved that the capacities of this new superconductors are high enough for designing superconducting materials for high field generation. In this talk, characteristics and potentials of iron-based superconductors are discussed from various viewpoints in an effort to understand the current status and future prospects. Currently, we are focusing on new family “1144” of iron based superconductors and have performed the magnetic measurements on high quality single crystal and polycrystal of CaKFe4As4 (1144) below the transition temperature, Tc ~ 35 K in the presence of applied magnetic field up to 16 T for out-plane (H//c) and in-plane (H//ab) directions and studied the superconducting properties and vortex dynamics behaviour of this new family. The single crystal exhibits a second magnetization peak (SMP) in the magnetic hysteresis loop only with H//c. The obtained Jc have extremely high value at low temperature that is almost magnetic field independent up to 15 T and are more than 100 times higher than that of any other iron based superconductors such as (Ba,K)Fe2As2 (122), Fe(Se,Te) (11), LiFeAs (1111), SmFeAs(O,F) (1111) and also MgB2, Nb3Sn, NbTi. The flux pinning force density (FP) has been obtained from the Jc-H isotherms at different temperatures and are scaled using the Dew-Hughes’s model to underline the pinning mechanism. The obtained pinning parameters suggest the existence of surface and point core pinning of the normal centres of core interaction. We have constructed the vortex phase diagram for this new 1144 family by comparing with other families of iron based superconductors. The obtained Jc phase diagram for this new family will also be discussed with iron based superconductors and MgB2. Our study depicts that this new family (1144) have high enough to be interesting for magnetic application in all iron based superconductors.