Switching-current reduction in perpendicular-anisotropy spin torque magnetic tunnel junctions

Magnetic tunnel junctions with the magnetization perpendicular to the plane of the layers can be switched between configurations with parallel or antiparallel magnetization of the layers using spin-polarized currents. Here we use finite-temperature micromagnetic modeling to study the switching behavior of such structures. In particular, we examine the effect of materials properties, such as magnetization density and magnetic anisotropy, on the current and time needed for the magnetization to switch from the parallel configuration to the antiparallel configuration. In addition, we study the possibility of lowering the required current density through a so-called exchange-spring effect in one of the magnetic layers. For circular devices of 70 nm diameter, we find a range of materials properties for which a current density of 2.6 MA/cm(2) can switch the magnetization configuration within 20 ns. However, for the parameters studied here, only small further reductions in the switching current density, to about 2.1 MA/cm(2), are possible, at a price of increasing the allowed switching time to 40 ns. (C) 2010 American Institute of Physics. [doi:10.1063/1.3457327]