Effects Of Different Oxidation Intercalation Layer On Anisotropy Magnetoresistance Of Permalloy Films

In this thesis, we explore approachs to improving anisotropic magnetoresistance andmagnetic properties of permalloy films, aiming at obtaining more thinner ones with betterpractical application of sensor and high sensitive magnetic heads. A series of Ni81Fe19magneticultra-thin films are prepared with a direct current magnetron sputtering system under appropriateconditions:Ta(4nm)/NiO(t)/Ni81Fe19(20nm)/NiO(t)/Ta(3nm);(Ni81Fe19)1-xNbx(y)/NiO(t)/Ni81Fe19(20nm)/NiO(t)/Nb(3nm). Influence of technological conditions are investigated, such as oxidationintercalation thickness, the percentage content of Nb atoms, buffer layer thickness and bufferlayer type, substrate temperature on the anisotropic magnetoresistance (AMR). The AMR ofpermalloy films are measured by non collinear four-point probe method. The surface topographyof Ni81Fe19films are measured by AFM. The crystal orientation and the grain size are measuredby XRD. Magnetic hysteresis loop is measured by FD-SMOKE-A. The experiment result showsmany interesting phenomena.(1) The thickness of oxidation intercalation has a great influence on AMR value. For thefilms Ta(4nm)/NiO(t)/Ni81Fe19(20nm)/NiO(t)/Ta(3nm), as t increasing, the AMR increases at0~4nm, then being stable when t is above2nm. Compared to the thin films without oxidationintercalation, the AMR value can be enhanced40%than the films without NiO layer.(2) The AMR depends significantly on substrate temperature. For the films Ta(4nm)/NiO(4nm)/Ni81Fe19(20nm)/NiO(4nm)/Ta(3nm) and (Ni81Fe19)80.7Nb19.3(2nm)/NiO(4nm)/Ni81Fe19(20nm)/NiO(4nm)/Nb(3nm), with the rise of substrate temperature, the AMR value increases firstly,then reaches to the maximum at450℃, When the substrate temperatures are higher than450℃,for the films (Ni81Fe19)80.7Nb19.3(2nm)/NiO(4nm)/Ni81Fe19(20nm)/NiO(4nm)/Nb(3nm), the AMRvalue becomes stable. however, while for the films Ta(4nm)/NiO(4nm)/Ni81Fe19(20nm)/NiO(4nm)/Ta(3nm), the AMR value becomes decrease with the substrate temperature rising after450℃.(3) The AMR of films (Ni81Fe19)1-xNbx(4nm)/Ni81Fe19(20nm)/Nb(3nm) depend on thepercentage content of Nb atoms. As a function of t, AMR value has a topped peak whenx=19.3%, and falls off quickly near the peak. It is confirmed that the maximum value is about 5.25%under the optimum conditions.(4) There is much influence of buffer layer thickness on anisotropic magnetoresistance ofpermalloy films. For the films (Ni81Fe19)80.7Nb19.3(y)/NiO(4nm)/Ni81Fe19(20nm)/NiO(4nm)/Nb(3nm), the AMR decreases firstly and then increases quickly with y increasing, with a maximumvalue at the2nm thickness of buffer layer. Compared to the thin films with Ta buffer layers, theAMR enhancement of60.6%is observed in the thin films with (Ni81Fe19)1-xNbx.X-ray diffraction of the films shows that (Ni81Fe19)1-xNbxbuffer layer causes theformation of large (111) textured crystal grains. The high temperature heating causes substrateclean again and improves its adhesion, which effectively reduce the stress distribution betweenthe membrane in intergranular and substrate and make the thin film defects decrease. Finally,The result leads the microstructure of films to dramatically change. According to the scatteringmechanism, it is explained that the bigger grain size makes the crystal boundary reduce, therebyweaken the electronic scattering. As a result, AMR value of the film to increase.The result shows that permalloy films with (Ni81Fe19)1-xNbxbuffer layer can adapt to thepractical application of sensor and magnetic recording instead of the Ta buffer layer. In addition,enhancing the AMR value by inserting the oxidation intercalation is of great significance to theresearch on permalloy films.