Spin-Transfer Torque — Magnetic Switching

Landau–Lifshitz–Gilbert–Slonczewski equation: current-driven magnetization reversal. Above the critical current I_c, spin-transfer torque overcomes damping.

Device Parameters

Critical current I_c
—
m_z (free layer)
—
Switching time
—
State
—
LLGS: dm/dt = −γ(m×H) + α(m×dm/dt) + η·I·(m×p×m)

I_c = (αeμ₀MₛV/ℏ)·(H_k/2)

Below I_c: stable precession
Above I_c: switching in ~ns