Transport properties and high upper critical field of a Fe(Se,Te) iron based superconductor

A Fe(Se,Te) iron based crystal has been studied using dc magnetic measurements as a function of temperature (T) and magnetic field (H). Firstly, the field dependence of the critical current density Jc has been extracted from the superconducting hysteresis loops m(H) at different temperatures within the Bean critical state model in order to obtain information about the transport properties of the sample. The knowledge of the critical current density values as a function of the field for temperatures near Tc allow us to determine the values and the behavior of the irreversibility field Hirr as a function of the temperature. On the other hand, by means of zero field cooling m(T) measurements at different magnetic fields, the upper critical field Hc2 has been evaluated as a function of the temperature. Both irreversibility field and upper critical field have been fitted by the equation H(T) = H(0)(1 − T/T*)n allowing us to obtain the values of the related parameters which are in good agreement with those found in literature for the IBS systems.