A large enhancement of magnetoresistance (MR) up to 6.0% has been observed in NiFe sandwiched by MgO layers, which is 50% larger than the highest MR (4%) in bulk materials. The great improvement of MR derives from the slight increase in corresponding resistivity change Delta rho and the great decrease in resistivity rho. The enhancement of Delta rho is attributed to the strengthened spin-dependent scattering of the interfacial conductive electrons but the contribution will be slight with the increase in NiFe thickness. The main contribution is from the significant decrease in rho, originating Surprisingly, this effect still exists when the NiFe thickness reaches 100 nm. Meanwhile, the oxide (MgO) layers inserted prevents the atomic interdiffusion of Ta and NiFe at the interfaces, which decreases the thickness of magnetic dead layer. (C) 2014 Elsevier B.V. All rights reserved.