Anomalous Hall Effect In Co/Pt And Co/Ni Multilayer Systems With Perpendicular Magnetic Anisotropy

In this thesis, I studied the magnetic properties of multilayer samples with perpendicular magnetic anisotropy (PMA) based on the Pt/Co/Pt sanwich and Co/Ni multilayer, and did some research on the anomalous Hall effect by using Hall circuit model.Pt/Co/Pt sandwich and Co/Ni multilayer samples with PMA were fabricated by magnetron sputtering, and magnetism and structure parameters were measured by VSM and Xrad etc. The anomalous Hall effect (AHE) in both systems was measured with both temperature and the theckness of non-magnetic layers, and the Hall circuit model was employed to study the AHE. For Pt/Co/Pt system, the anomalous Hall coefficient of Co layer (including Co/Pt interfaces) was deduced from the measured Hall voltage signal in the Hall shunting circuit. First, we changed the thickness of Pt cap layer, and studied the scaling law for anomalous Hall coefficient of Co layer when other parameters unchanged. Considering the spin Hall effect in Pt layer, we proposed the influence of spin Hall effect in Pt layer to anomalous Hall effect in Co layer and Co/Pt interfaces. Furthermore, we verified the consistency of Hall circuit model by reversing the thickness of cap and bottom Pt layers in the sandwich structure. Plus, the temperature dependence of anomalous Hall coefficient of Co layer was obtained from the measured results. By contrasting the relevant results in literatures, the role of non-magnetic Pt layer in the Pt/Co/Pt samples could be understood. In Co/Ni multilayer system, the contribution of ferromagnetic part, [Co/Ni]N layer, was deduced from the measured results, and the evidence shows that the anomalous Hall coefficient of [Co/Ni]N layer increases with tempereture. Also, the some parameters just like the anomalous Hall coefficient in zero temperature could be obtained. The relativity between the periodity N of [Co/Ni]N layer and the scattering independent term of anomalous Hall coefficient indicates that the anomalous Hall coefficient of Co/Ni interfaces has opposite sign of that in Co and Ni bulk.In addition, we also obtained that the ratio of Hall current in longitudinal direction and the injected current is non-monotonic with temperature. Our research provides important insights to the systems with both strong spin-orbit coupled interfaces like Co/Pt and 3d-3d FM interfaces like Co/Ni.