Interface-assisted magnetoresistance behavior for ultrathin NiFe films

•We studied magnetic and electric transport properties of ultrathin NiFe films.•Interface chemical states have strong influence on MR in NiFe films.•Crystallization of the top MgO layer has influence on MR in NiFe films.

Interface-assisted magnetoresistance (MR) behavior has been studied in Ta/MgO/NiFe/MgO/Ta multilayers by inserting a Mg metal layer between the NiFe layer and the top MgO layer. It is shown that MR ratio is about 31% larger than that in the films without Mg insertion. X-ray photoelectron spectroscopy and high resolution transmission electron microscope analyses show that the enhanced MR is primarily ascribed to effective control of chemical states at the NiFe/MgO interface and crystallization of the top MgO layer.