Effects of Pnictogen Atmosphere Annealing on Fe1+yTe0.6Se0.4

Abstract

It has been clarified that bulk superconductivity in Fe1+yTe0.6Se0.4 can be induced by annealing in an appropriate atmosphere to remove the harmful effects of excess iron. In order to clarify the details of the annealing process, we studied the changes in the physical properties and reaction products of Fe1+yTe0.6Se0.4 annealed in pnictogen (P, As, Sb) atmospheres. Crystals annealed in a pnictogen atmosphere show bulk superconductivity and the values of Tc and Jc are about 14 K and (2–4) × 105 A/cm2 (2 K, self-field), respectively. It is also found that the reaction rate increases with the increase in the saturated vapor pressure of the pnictogen. Unexpectedly, the reaction products of Fe1+yTe0.6Se0.4 after annealing in a P atmosphere mainly consist of FeTe2. In addition, the amount of P required to obtain the optimal Tc is much smaller than the amount of excess iron, which is similar to the case of oxygen annealing. P, oxygen, and to some extent As could serve as catalysts to form FeTe2 to remove excess ...