Precession coupled spin current in spin torque driven magnetic tunnel junctions

A spin-torque switchable magnetic tunnel junction contains two ferromagnetic electrodes across a barrier that supports spin-polarized current. The induced switching of its more agile, or “free” layer provides the “write” mechanism. Often dynamics non-switching “reference” is also important. Here, we illustrate such involving both free and reference layers by using an exchange-coupled two-macrospin-moment numerical model, described set Landau–Lifshitz–Gilbert (LLG) equations, together with stochastic Langevin-field for finite temperature. Damping-like spin-transfer torque included moments. In steady-state, coupled precession shown to reduce effective spin-current delivered due precessional resonant back flow. This back-flow spin current preferentially affects parallel state dynamics. It not directly related layer’s thermal stability, nor threshold, as determined total anisotropy energy volume. Rather, reduction relates primarily matching frequency between free- reference-layer. Therefore, desirable materials choice avoid fields giving similar dynamic frequencies, so prevent resonance-related loss.