A new approach for improving global critical current density in Fe(Se0.5Te0.5) polycrystalline materials

A novel method to prepare bulk Fe.Se0:5Te0:5/ samples is presented, based on a melting and a subsequent annealing treatment. With respect to the standard sintering, it produces much more homogeneous and denser samples, characterized by large well interconnected grains. The resulting samples exhibit optimal critical temperature, sharp resistive and magnetic transitions, large magnetic hysteresis loops and high critical fields. Interestingly, the global critical current density is much enhanced as to the values reported in the literature for bulk samples of the same 11 family, about 103 A cm2 at zero field at 4.2 K, as assessed by magnetic, transport and-optical techniques. Even more importantly, its field dependence turns out to be very, such that at 7 T it is suppressed only by a factor 2.