# Optimizing Perpendicular Magnetic Anisotropy in MgO/CoFeB Structures Through Ultrathin CoFeB-Enhanced Ta Capping Layers

## TL;DR

Researchers improved magnetic properties in a material structure by adding a thin layer, leading to better performance for spintronic devices.

## Contribution

A novel ultrathin CoFeB insertion layer is introduced to enhance perpendicular magnetic anisotropy in MgO/CoFeB structures.

## Key findings

- An ultrathin CoFeB layer improves PMA by enhancing Fe–O hybridization and suppressing diffusion.
- Postannealing achieves an interfacial anisotropy constant (Ki) of 3.8 erg/cm², the highest reported for similar structures.
- The CoFeB insertion layer maintains structural integrity and optimal oxidation at the interface.

## Abstract

This study presents an innovative approach to optimizing
perpendicular
magnetic anisotropy (PMA) in CoFeB/MgO structures through the strategic
insertion of an ultrathin CoFeB layer between the top capping layer
(Ta or Mo) and the CoFeB/MgO stack. Adding a 0.43 nm CoFeB insertion
layer significantly enhances PMA by improving Fe–O hybridization,
suppressing interfacial diffusion, and stabilizing MgO crystallinity.
Postannealing at 400 °C, the CoFeB (free)/MgO (capping)/CoFeB
(0.43 nm insertion layer)/Ta (top capping) configuration demonstrates
superior performance, achieving an interfacial anisotropy constant
(Ki) of 3.8 erg/cm2, the highest
reported for similar structures under these conditions. Advanced analyses
using high-resolution transmission electron microscopy and X-ray photoelectron
spectroscopy reveal that the ultrathin CoFeB insertion effectively
mitigates diffusion from the top capping layer, maintaining optimal
oxidation and structural integrity at the interface. These findings
not only deepen the understanding of PMA enhancement mechanisms but
also provide a thermally stable, high-performance solution compatible
with CMOS back-end-of-line processing. This work underscores the potential
of interfacial engineering for advancing next-generation spintronic
technologies.