Upper critical field and coefficient of magnetoresistance in NdBa2Cu3O7−y and NdBa2Cu2.9Mn0.1O7−y

► The magnetoresistance of Nd-123 and Mn doped Nd-123 has been studied. ► The upper critical field and coefficient of magnetoresistance have been extracted. ► Change in the coherence length has been observed. ► The impact of Mn substitution has been discussed. We study the magnetotransport properties of NdBa2Cu3O7−y (NBCO) and NdBa2Cu2.9Mn0.1O7−y (NBCMO) superconductors. The shifting in the transition curves at several magnetic fields has been used to obtain the H–T phase diagram. The upper critical fields, Hc2(0) and coherence lengths, ξ of both compounds have been extracted. The coherence length decreases in NBCMO in comparison to that of the NBCO. The change in the coherence length has been attributed mostly to changes in the resistive paths induced by Mn. The coefficients of the magnetoresistance, β, of both NBCO and NBCMO in the vicinity of the transition region have been extracted using the variation of Ln (Δρ/ρ0) as a function of Ln (H2), where Δρ=ρ(T,H)−ρ(T,0) is the change in the resistivity by the applied magnetic field at any temperature, T. ρ0=ρ (T,0), represents the resistivity at zero magnetic field.