Characterization of Domain Switching Behavior of MTJ Cells Using Magnetic Force Microscopy (MFM) and R–H Loop Analysis

Correlation between electrical and magnetic properties of magnetic tunnel junctions (MTJ) for magnetic random access memory (MRAM) was studied. The MTJ ($\hbox{Ta/NiFeCr/} \hbox{PtMn/CoFe/Ru/CoFe/Al}_{2}\hbox{O}_{3}\hbox{/CoFe/NiFe/Ta}$ ) was analyzed by utilizing R–H loops and MFM images. We verified that a kink in an R–H loop comes from a vortex domain of free layer. In addition, we also observed a close relationship between a domain switching behavior and an irregular R–H curve. These results would be useful for the characterization of the MTJ cell, thereby optimizing the process to realize an ultrahigh density MRAM.