| This thesis will describe the design and development of a new kind of nonvolatile random access memory: magnetoresistive random access memory (MRAM). By utilizing giant magnetoresistive effect (GMR), spin valve effect, or spin tunneling effect, this memory has the potential to be radiation hard, very dense (comparable to DRAM) and very fast (comparable to SRAM). We utilize micromagnetic modeling to study the most important aspects of memory devices: micromagnetic behaviors of submicron size thin film elements and their critical roles in determining the device performance characteristics. Switching behaviors such as magnetization switching process and switching field of patterned submicron size elements are studied. It is found that the magnetic switching behaviors of the patterned elements are strongly influenced by their geometric shape, film thickness, edge roughness, as well as edge domain configurations. The design principles and operation characteristics of spin valve memory elements and pseudo spin valve memory elements are presented. For the linear mode memory devices, the edge demagnetization effect and interlayer magnetostatic interaction are the two most concerned issues since they are the main sources that cause the instability of the performance. Finally, a memory device with circular shape elements is designed and investigated. Since the magnetic flux is continual in a circular domain, the end domain effects as well as interlayer magnetostatic coupling can be completely eliminated in circular elements. With the presence of special designed wordline pairs, the performance of the circular memory elements can be very reliable and repeatable. |
