CoFeB Thickness Dependence of Thermal Stability Factor in CoFeB/MgO Perpendicular Magnetic Tunnel Junctions

TL;DR

This study investigates how the thermal stability factor in CoFeB/MgO perpendicular magnetic tunnel junctions depends on the thickness of the CoFeB layer, revealing a linear increase with thickness and size independence.

Contribution

It demonstrates that the thermal stability factor linearly depends on CoFeB thickness and is unaffected by junction size, supported by a nucleation-based magnetization reversal model.

Findings

Thermal stability factor is size-independent in the studied range.

Delta increases linearly with CoFeB thickness.

Nucleation model explains the linear dependence.

Abstract

Thermal stability factor (delta) of recording layer was studied in perpendicular anisotropy CoFeB/MgO magnetic tunnel junctions (p-MTJs) with various CoFeB recording layer thicknesses and junction sizes. In all series of p-MTJs with different thicknesses, delta is virtually independent of the junction sizes of 48-81 nm in diameter. The values of delta increase linearly with increasing the recording layer thickness. The slope of the linear fit is explained well by a model based on nucleation type magnetization reversal.