Magnetic properties of very thin single and multilayer NiFeCo and CoFe films deposited by sputtering

Abstract

As the size of the giant magneto resistive (GMR) devices continues to decrease into submicrometer regime, the demagnetizing field from the magnetic layers will increase to very high values, prohibiting switching with a reasonably small current. The most feasible way to reduce it is to make the magnetic layers thinner. Single layers of NiFeCo and CoFe films as well as multilayers consisting of these with various underlayers have been deposited by rf diode sputtering in a magnetic field. NiFeCo becomes nonmagnetic at 15, 10, and 6 Å when using Ta, Si3N4, and Cu underlayers, respectively. The magnetization of NiFeCo films sandwiched with Cu decreases as the films become thinner, indicating that about one atomic layer loses its magnetic moment at each interface with Cu. The induced magnetic anisotropy is a strong function of the NiFeCo film thickness, changing from 7 Oe for 20 Å to 17 Oe for 100 Å. CoFe films lose very little magnetic moment at the interfaces with Cu. Multilayers of [NiFeCo/Cu/CoFe/Cu] with different Cu underlayer thickness have been made and the magnetic and GMR properties show a strong dependence on the Cu buffer layer thickness due to different interface roughnesses. With proper designing of the interfaces, these very thin magnetic films have high potential for ultrahigh-density magnetic memory and other applications.