Deep subnanosecond spin torque switching in magnetic tunnel junctions with combined in-plane and perpendicular polarizers

Abstract

We show that adding a perpendicular polarizer to a conventional spin torque memory element with an in-plane free layer and an in-plane polarizer can significantly increase the write speed and decrease the write energy of the element. We demonstrate the operation of such spin torque memory elements with write energies of 0.4 pJ and write times of 0.12 ns.

Electric field control of magnetism using BiFeO3-based heterostructures

“…Electronic mail: jth247@cornell.edu consumption. 13,14 As an example of the energy consumption of such a device, a state of the art STT device requires a voltage pulse of several hundred millivolts (0.7 V) and 120 ps 14 -500 ps 13 in duration through a 60-70 nm  180 nm device leading to energy dissipation per unit area per switch of 3-4 mJ/cm 2 . The effort to reduce this energy cost has led to the pursuit of mechanisms by which magnetic anisotropy and magnetization direction can be tailored with an applied electric field, rather than electrical current, where, in an ideal case, the energy dissipation per unit area can be estimated to be at least an order of magnitude smaller.…”

Irreversible magnetization switching using surface acoustic waves

“…If the precession amplitude is sufficiently large, the magnetization can switch to another potential valley, where it will remain if the perturbation lasts an odd multiple of half the precession period 17 , or if damping eventually prevents M from oscillating between the two minima ("ringing" phenomenon). This mechanism has for instance being suggested for micro-wave assisted switching at a head field significantly below the medium coercivity 19 or for subnanosecond spin torque switching in magnetic tunnel junctions 20 .…”

Magnetic Tunnel Junctions and Their Applications in Nonvolatile Circuits

“…Only the use of magnetoelectric effects, where charge currents are greatly reduced or eliminated, allows the energy to reach the levels of CMOS, making both the NVM and the CMOS limited in energy by only capacitive losses. It is worth noting that, similarly to the STT effect, the speed for switching an MTJ can be increased by moving from the thermally activated to the precessional regime [66,75], reducing the write time still along the line between HP and LP CMOS. It should be stressed that reducing the write energy of the MTJ down to the level of CMOS is a requirement for nonvolatile circuits where the MTJs switch frequently; otherwise, the advantages of reduction of standby power would be overshadowed by the drastic increase in dynamic power.…”

“…Consequently, the switching speed is generally limited to~1 ns [65,66], limiting the range of application of the nonvolatile circuits to applications that do not require switching at GHz speeds. However, the switching speed of in-plane MTJ can be improved by one order of magnitude (up to the ferromagnetic resonance frequency of the free layer) by including an additional out-of-plane polarizer, which can eliminate the initial incubation due to the perpendicular polarization of the spins compared to the free layer.…”

“…However, the switching speed of in-plane MTJ can be improved by one order of magnitude (up to the ferromagnetic resonance frequency of the free layer) by including an additional out-of-plane polarizer, which can eliminate the initial incubation due to the perpendicular polarization of the spins compared to the free layer. The latter approach is known as an orthogonal MTJ device [65][66][67] and shows switching times~100 ps, but usually with a penalty in terms of dynamic write energy [66].…”