Different Buffer Layer On The Permalloy Thin Film Anisotropic Magnetoresistance Effect

In this thesis, we explore the approach to improving anisotropicmagnetoresistance and magnetic properties of permalloy films when the thickness ofpermalloy films is more thinner for adapting to the practical application of sensor andhigh sensitive magnetic heads. A series of films with different buffer layers areprepared with a direct current magnetron sputtering system under appropriateconditions:Ta(y)/Ni81Fe19(20nm)/Ta(3nm);Ta(y)/ZnO(t)/Ni81Fe19(20nm)/ZnO(t)/Ta(3nm);(Ni81Fe19)1-xNbx(y)/Ni81Fe19(20nm)/Ta(3nm).Influence of technological conditionssuch as substrate temperature, buffer layer thickness, the percentage content of Nbatoms and oxidation intercalation on AMR are investigated. The AMR of permalloyfilms are measured by non collinear four-point probe method. The crystal orientationand the grain size are measured by XRD. The surface topography of Ni81Fe19filmsare measured by AFM. The experiment result shows that:(1) The AMR depends significantly on substrate temperature. For the filmsTa(y)/Ni81Fe19(20nm)/Ta(3nm) and (Ni81Fe19)1-xNbx(y)/Ni81Fe19(20nm)/Ta(3nm), withincreasing substrate temperature, the AMR value increases firstly, then reaches to themaximum at450℃, When the substrate temperatures are higher than450℃, the AMRvalue becomes stable. Similarly, for the films ZnO(t)/Ni81Fe19(20nm)/ZnO(t)/Ta(3nm),with increasing substrate temperature, the AMR value increases, then reaches to themaximum at400℃, however, the AMR value becomes decrease with the substratetemperature rising after400℃.(2) There is much influence of buffer layer thickness on anisotropicmagnetoresistance of permalloy films. For the films Ta(y)/Ni81Fe19(20nm)/Ta(3nm)and (Ni81Fe19)1-xNbx(y)/Ni81Fe19(20nm)/Ta(3nm), the AMR increases firstly and thendecreases quickly with y increasing, it has a maximum value at the4.0nm thicknessof buffer layer. Compared to the thin films with Ta buffer layers, the AMRenhancement of31%is observed in the thin films with (Ni81Fe19)1-xNbx.(3) The AMR and microstructure depend significantly on the percentage contentof Nb atoms. As a function of x, AMR value has a topped peak when x=19.3%, andfalls off quickly near the peak. It is confirmed that the maximum value is about3.76%under the optimum conditions. X-ray diffraction of the films shows that(Ni81Fe19)1-xNbxbuffer layer causes the formation of large (111) textured crystalgrains. According to the scattering mechanism, it is explained that the bigger grainsize makes the crystal boundary reduce, thereby leads the electronic scattering toweaken. Due to this reason, it causes AMR value of the film to increase.(4) The thickness of oxidation intercalation has a great influence on AMR value.For the films Ta(ynm)/ZnO(t)/Ni81Fe19(20nm)/ZnO(t)/Ta(3nm), with t increasing, theAMR decreases firstly at0~0.5nm and then increases at0.5~2nm, then the AMRvalue becomes stable when t is above2nm. Compared to the thin films withoutoxidation intercalation, AMR value has a very significant increase with oxidationintercalation.The result shows that permalloy films with (Ni81Fe19)1-xNbxbuffer layer canadapt to the practical application of sensor and magnetic recording instead of the Ta buffer layer, because of its high anisotropic magnetoresistance and well magneticproperties. In addition, enhancing the AMR value by inserting the oxidationintercalation is of great significance to the research on permalloy films.