Thermal Effects on Damping Determination of Perpendicular MRAM Devices by Spin-Torque Ferromagnetic Resonance

TL;DR

This study investigates how thermal agitation and device patterning affect damping measurements in small perpendicular MRAM cells, revealing that thermal effects are fundamental and that patterning causes increased damping due to edge damage.

Contribution

It demonstrates that thermal effects influence damping measurements in MRAM devices and distinguishes these from true damping increases caused by patterning damage.

Findings

Thermal agitation enhances apparent damping in sub-55nm MRAM cells.

Device-level damping exceeds film-level damping, especially in smaller cells.

Edge damage from patterning contributes to increased damping.

Abstract

We report device level damping measurements using spin-torque driven ferromagnetic resonance on perpendicular magnetic random-access memory (MRAM) cells. It is shown that thermal agitation enhances the apparent damping for cells smaller than about 55 nm. The effect is fundamental and does not reflect a true damping increase. In addition to the thermal effect, it is still found that device level damping is higher than film level damping and increases with decreasing cell size. This is attributed to edge damage caused by device patterning.