Thermally activated flux creep in the Bi1.66Pb0.34Sr2Ca2−xMgxCu3Oy superconductors

A systematic study of the magnetoresistance of Bi1.66Pb0.34Sr2Ca2−xMgxCu3Oy (x = 0, 0.2 and 0.4) samples has been studied within the thermally activated flux creep model. Under lower applied magnetic field, the calculated flux pinning energies, U(H) and intergranular upper critical field, Hc2 decreases by increasing the amount of Mg. The higher electronegativity of Mg in the unit cell promotes more intake of oxygen in the material, and the grain boundaries are in more over-doped regime. These over-doped regions reduce the intergranular coupling and increases weak link behavior of Mg doped samples.