We have performed micromagnetic simulations for the design of toggle magnetoresistive random access memory (MRAM) cells to make the operating field as low as possible while keeping a reasonable margin and thermal stability. The memory cells are composed of weakly coupled synthetic antiferromagnets. The cells are diamond-shaped to suppress the formation of edge domains, which increase the operating field. The adverse effect of the diamond shape making the remanent state too stable is prevented by trimming the sharp points. The optimization of the trimming allows us to reduce the operating field and offer a pathway for realizing high-density toggle MRAM. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3104788]