MTJ consists of two ferromagnetic (FM) electrodes separated by an insulating layer that is thin enough to allow electrons to tunnel across. It has a rich background in physics and also shows much promise for applications as varied as non-volatile magnetic random access memory (MRAM), hard drive read heads, and magnetic field sensors. Our previous studied were based on the effect of bias dependence of tunnel magneto-resistance (TMR). Quantum mechanical model was also utilized to well explain the observed results. We plan to study the effect of dislocations or defects on TMR both experimentally and theoretically in the next step.