Reduction of switching current by spin transfer torque effect in perpendicular anisotropy magnetoresistive devices (invited)

Abstract

Spin transfer torque-based magnetic random access memory with perpendicular magnetic anisotropy (PMA) provides better scalability and lower power consumption compared to those with in-plane anisotropy. Spin transfer torque switching in magnetoresistive spin valves with PMA is investigated. The hard layer is made of (Co/Pd) multilayer, whereas the soft layer is a lamination of (CoFe/Pd) and (Co/Pd). By the insertion of an in-plane spin polarizer adjacent to the perpendicular anisotropy free layer, thus creating a modified-dual spin valve, a significant reduction of about 40% in the current density required for spin torque transfer switching was observed. By using a spin polarized current with different pulse widths down to 10 ns, the barrier energy EB in 100-nm-diameter devices was found to be reduced from 1.1 to 0.43 eV. Besides the reduction of switching current density in a device with PMA, the new structure shows a clear increase in magnetization switching speed as revealed by micromagnetic simulation.

Influence of device geometry on the non-volatile magnetic flip flop characteristics

“…The linear behavior for the thicker free layers is consistent with a saturated demagnetization factor N z and the linearly growing volume when increasing the layer thickness [25]. On the other hand for thinner free layers the demagnetization factor is not saturated as compared to thick layers and starts to grow when the thickness is decreased.…”

“…It can also be observed that for thicker films the linear fit matches very well (linear fit → dashed line, simulation data → solid line), while for a thickness below 2nm a shorter switching time than predicted by the linear fit is found. In order to explain this behavior we assume an exponential dependence of the switching time t ∝ exp(E/k B T ) [24] on the thermal stability barrier E described by [25]:…”

Spin-wave thermal population as temperature probe in magnetic tunnel junctions

“…A strong research effort is currently done within the spintronics community to obtain ever improved magnetic properties 1,2 for optimal utilization in integrated devices like sensors and memories 3 which often rely on Magnetic Tunnel Junctions (MTJ). Often overlooked, the evolution of the magnetic properties with temperature is crucial for achieving high performance MTJ.…”

Thick CoFeB with perpendicular magnetic anisotropy in CoFeB-MgO based magnetic tunnel junction

“…[8][9][10][11][12] However, in order to implement this system into real application, has to be further improved while lowering the J C . Recently, there have been several efforts in reducing J C of CoFeB-MgO MTJ by incorporating insertion layer 13 for example or by employing electric field (E) assisted switching.…”