Parameterization of Multi Band Model of Critical Magnetic Fields for the Iron based Superconductor Ba(Fe_1-xNi_x)₂As₂

In this study, the mathematical expression of temperature dependence upper critical magnetic field (HSUBc2/SUB), angle dependence of upper critical magnetic field (HSUBc2/SUB), and temperature dependence of Ginzburg-Landau (GL) characteristics were investigated. The parameters were computed by using two band Ginzburg-Landau (GL) phenomenological model for Ba(FeSUB1-x/SUBNiSUBx/SUB)₂As₂ iron based superconductor. Application of very small external magnetic field at low temperature to nickel doped BaFe₂As₂ changes to Ba(FeSUB1-x/SUBNiSUBx/SUB)₂As₂ iron based superconductor at a critical temperature of 19.5 K. The phase diagrams of the two upper-critical field and GL characteristics length were plotted as a function of angle and temperature for Ba(FeSUB1-x/SUBNiSUBx/SUB)₂As₂ iron based superconductor using the experimental values. The phase diagram shows the linear dependence of upper critical magnetic field parallel HSUP∥c/SUPSUBc2/SUB and perpendicular (HSUP⊥c/SUPSUBc2/SUB) with temperature (T). Correspondingly, the phase diagrams of the upper critical field (HSUBc2/SUB(θ)) versus the angle (θ) were plotted. The parallel and perpendicular to the symmetry axis of coherence length (ξSUBGL/SUB(T)) and penetration depth (λSUBGL/SUB(T)) versus temperature were plotted. In these plots both parameters are increased with increasing temperature and diverges at the critical temperature for the superconductor Ba(FeSUB1-x/SUBNiSUBx/SUB)₂As₂. This theoretical investigation was found to be in agreement with the obtained experimental results.