Coherent control of nanomagnet dynamics via ultrafast spin torque pulses

TL;DR

This paper demonstrates the coherent control of nanomagnet dynamics using ultrafast spin torque pulses, enabling precise manipulation of magnetization states for advanced spintronic applications at room temperature.

Contribution

It introduces a method to control nanomagnet dynamics with 30 ps current pulses, achieving tunable switching and coherence at room temperature, advancing spintronic device capabilities.

Findings

Magnetization can be coherently manipulated with 30 ps pulses.

Switching probability is tunable via pulse timing.

Magnetization coherence persists over 1 ns at room temperature.

Abstract

The magnetization orientation of a nanoscale ferromagnet can be manipulated using an electric current via the spin transfer effect. Time domain measurements of nanopillar devices at low temperatures have directly shown that magnetization dynamics and reversal occur coherently over a timescale of nanoseconds. By adjusting the shape of a spin torque waveform over a timescale comparable to the free precession period (100-400 ps), control of the magnetization dynamics in nanopillar devices should be possible. Here we report coherent control of the free layer magnetization in nanopillar devices using a pair of current pulses as narrow as 30 ps with adjustable amplitudes and delay. We show that the switching probability can be tuned over a broad range by timing the current pulses with the underlying free-precession orbits, and that the magnetization evolution remains coherent for more than 1 ns even at room temperature. Furthermore, we can selectively induce transitions along free-precession orbits and thereby manipulate the free magnetic moment motion. We expect this technique will be adopted for further elucidating the dynamics and dissipation processes in nanomagnets, and will provide an alternative for spin torque driven spintronic devices, such as resonantly pumping microwave oscillators, and ultimately, for efficient reversal of memory bits in magnetic random access memory (MRAM).