Jang Eun Lee

Enhanced switching current density due to resonant precession in current-induced magnetization switching

Micromagnetic investigation was performed on the influence of neighboring cells in a conventional rectangular array to the switching current density (Jc) in the current-induced magnetization switching. We found that the Jc was increased regardless of the relative switching direction to the overall stray field. It is because the precession of the magnetization in the switching cell induces a resonant precession in neighboring cells through magnetostatic interaction. The resonant precession disturbs a fast reversal and results in the enhanced Jc for a fixed pulse width. The enhancement increases as the distance between the cells decreases. Here we proposed a zigzag array which significantly suppresses the enhancement of Jc due to the resonant precession.

Switching phase diagrams of current-induced magnetization switching in asymmetric MgO-based magnetic tunnel junctions

We investigated the effect of the free-layer composition and the pattern size of magnetic cell on current-induced magnetization switching in asymmetric MgO-based magnetic tunnel junctions. We found that the normalized switching phase diagrams (SPDs) measured at low temperature are mostly determined by the material composition of ferromagnetic electrodes but are not much sensitive to the intrinsic energy barrier and the anisotropy field of the sample. This experimental result indicates that the normalized SPD can be used to study the fundamental characteristics of spin-transfer torque.

Thermal stability of MTJ using Zr capping layer

The simple stacking structure such as [Sub/Zr/AlO/sub x//NiFe (or CoFeB)/capping layer] was prepared to investigate the changes of magnetic properties of free layer with annealing temperature. Ta, Ru, or Zr was used as the capping layer. Samples were annealed in a vacuum (below 1/spl times/10/sup -6/ Torr) for 1 hour under a magnetic field of 10 KOe. The magnetic properties were measured using vibrating sample magnetometer in sample with 1/spl times/1 cm/sup 2/ area. The changes of the coupling field between the pinned layers through Ru as a function of annealing temperature for various pinned layer materials were also studied.