Enhancement of anisotropic magnetoresistance in MgO/NiFe/MgO trilayers via NiFe nanoparticles in MgO layers

Abstract

MgO/NiFe/MgO trilayers, the new development in highly sensitive anisotropic magnetoresistance (AMR) sensor film materials, exhibit severely reduced magnetoresistance ratios at small NiFe thicknesses. By inserting ultrathin NiFe(І) layers into the top and bottom MgO layers of MgO/NiFe/MgO trilayers, films with a structure of MgO/NiFe(І)/MgO/NiFe/MgO/NiFe(І)/MgO were designed and synthesized. The AMR value can be significantly enhanced for thin NiFe films due to the improved specular reflections of electrons at both NiFe/MgO interfaces. For a thin NiFe film with the structure of MgO/NiFe(І)(1.5 nm)/MgO/NiFe(5 nm)/MgO/NiFe(І)(1.5 nm)/MgO, the AMR value was greatly enhanced to as high as 2.71%, an increase of 37% over MgO/NiFe(5 nm)/MgO film.