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 process and a subsequent annealing treatment. With respect to the standard sintering technique, it produces much more homogeneous and denser samples, characterized by large and well interconnected grains. The resulting samples exhibit optimal critical temperature values, sharp resistive and magnetic transitions, large magnetic hysteresis loops and high upper critical fields. Interestingly, the global critical current density is much enhanced as compared to the values reported in the literature for bulk samples of the same 11 family, reaching about 10(3) A cm(-2) at zero field at 4.2 K, as assessed by magnetic, transport and magneto-optical techniques. Even more importantly, its field dependence turns out to be very weak, such that at mu H-0 = 7 T it is suppressed only by a factor similar to 2.