Broadband Ferromagnetic Resonance Linewidth Measurement of Magnetic Tunnel Junction Multilayers

TL;DR

This study uses broadband ferromagnetic resonance linewidth measurements of magnetic tunnel junctions to diagnose magnetic quality, revealing correlations with magnetic disorder, hysteresis, and noise, and showing how annealing affects magnetic properties.

Contribution

It introduces a simple FMR linewidth measurement method to assess magnetic disorder and quality in magnetic tunnel junction multilayers, linking it to magnetic hysteresis and noise.

Findings

FMR linewidth increases near free and pinned layer reversal fields.

Postannealing alters the free layer FMR linewidth, indicating changes in magnetic disorder.

FMR linewidth correlates with magnetic hysteresis and low-frequency noise.

Abstract

The broadband ferromagnetic resonance (FMR) linewidth of the free layer of magnetic tunnel junctions is used as a simple diagnostic of the quality of the magnetic structure. The FMR linewidth increases near the field regions of free layer reversal and pinned layer reversal, and this increase correlates with an increase in magnetic hysteresis in unpatterned films, low frequency noise in patterned devices, and previous observations of magnetic domain ripple by use of Lorentz microscopy. Postannealing changes the free layer FMR linewidth indicating that considerable magnetic disorder, originating in the exchange-biased pinned layer, is transferred to the free layer.