Study of soft magnetic thin films and patterned devices with MOKE imaging technique

While the conventional microelectronic integrated circuits based on the electron charge are approaching the theoretical limitation in foreseeable future, next generation nonvolatile logic units based on electron spin have potential to build logic networks of low-power consumption. Central to this work is to investigate the magnetic properties of soft magnetic materials and develop a method for in-memory computing based on patterned soft magnetic materials logic units.
The mainly result were carried out by Magneto-optical Kerr effect (MOKE) microscopy. By inverting the growth order, the amount of defects can be artificially tuned, and skyrmions are shown to be preferentially formed in samples with more defects. The stable region and the density of the skyrmions can be efficiently controlled in the return magnetization loops by utilizing first-order reversal curves (FORCs). The major contribution of these findings establish a general internal link from sample preparation to skyrmion generation and provides a general method for controlling skyrmion density. Next, the temperature-dependent magnetic properties of MgO/CoFeB/Ta thin films have been investigated. The perpendicular magnetic anisotropy (PMA) gradient in MgO/CoFeB/Ta thin films via the temperature gradient generation sample stage has been studied. This study provides a new easy method to create a PMA gradient that will contribute to the simplification of field-free spintronic devices. Eventually, Y-shaped NiFe nanowire has been investigated. The quasi-static micromagnetic simulations correspond to the experimental results and reveal the principle of device operations. The use of programmable logic units and potential applications for in-memory computing have been further extended based on this nanostructure. The major contribution of this part proposes a feasible paradigm for in-memory computing programmable logic gate, which can significantly reduce the complexity of conventional logic circuits. The results conclusion and discussion for the future works are proposed in the final chapter.