Inductive determination of the optimum tunnel barrier thickness in magnetic tunnelling junction stacks for spin torque memory applications

TL;DR

This study uses inductive microwave magnetometry to determine the optimal MgO tunnel barrier thickness in magnetic tunnel junctions, crucial for efficient spin torque memory devices.

Contribution

It introduces a fast, inductive measurement method to identify the optimal tunnel barrier thickness for spin torque memory applications without lithography.

Findings

Increased damping observed below a certain barrier thickness

Optimal barrier thickness range identified for reversible magnetization switching

Method enables rapid, lithography-free determination of tunnel barrier quality

Abstract

We use pulsed inductive microwave magnetometry to study the precessional magnetization dynamics of the free layer in CoFeB/MgO/CoFeB based magnetic tunnelling junction stacks with varying MgO barrier thickness. From the field dependence of the precession frequency we are able to derive the uniaxial anisotropy energy and the exchange coupling between the free and the pinned layer. Furthermore the field dependence of the effective damping parameter is derived. Below a certain threshold barrier thickness we observe an increased effective damping for antiparallel orientation of free and pinned layer which would inhibit reversible low current density spin torque magnetization reversal. Such inductive measurements, in combination with wafer probe station based magneto transport experiments, allow a fast determination of the optimum tunnel barrier thickness range for spin torque memory applications in a lithography free process.