Micromagnetic Studies of Lateral TMR Memory Cell Driven by Spin Polarized Current or by Magnetic Field

The switching properties of an elliptical TMR memory cell Co₇₀Fe₃₀(PL1)/Ru/Co₆₀Fe₂₀B₂₀(PL2)/MgO/Co₆₀Fe₂₀B₂₀(FL), by magnetic field or by current, are studied with micromagnetic simulation. The switching characteristic of FL is understood by introducing reduced saturation magnetization at the edge of the elliptical trilayer structures. The polycrystalline microstructure is also important in the simulations. The uncompensated demagnetization field generated by the pinned layer can cause asymmetry to the R-H loop of magnetic field reversal case; and under certain conditions, it can lead to the symmetric switching current in the R-J loop for the spin polarized current reversal case. The reduced saturation magnetization at the edge and the separate treating of crystal grains and grain boundaries are essential factors in the good agreement between simulated and experimental R-H and R-J loops.