Enhancement of the magnetic field sensitivity in Al2O3 encapsulated NiFe films with anisotropic magnetoresistance

Abstract

The anisotropic magnetoresistance value (ΔR/R) and magnetic field sensitivity (Sv) of NiFe films can be remarkably enhanced by using Al2O3 encapsulation, and the Sv is comparable to that of a spin valve. For an ultrathin NiFe film with the structure of Ta/Al2O3/NiFe/Al2O3/Ta, the Al2O3 layers suppress the formation of the magnetic dead layers and the interdiffusions between the NiFe layer and Ta layers, and decrease the current shunting of the Ta layers. More importantly, the flatter Al2O3/NiFe and NiFe/Al2O3 interfaces can significantly enhance the specular reflection of conduction electrons and lead to a higher ΔR/R. In addition, the formations of the NiFe (111) texture and the columnar grains by annealing can also increase the ΔR/R.