A micromagnetic study of the switching dynamics of the BiFeO$_3$/CoFe heterojunction

TL;DR

This study models the switching dynamics of a BiFeO3/CoFe heterojunction, quantifies key parameters like interface exchange coupling, and suggests ways to improve stability and switching success rate based on theoretical and experimental analysis.

Contribution

First quantitative extraction of the interface exchange coupling coefficient J_int from experiments in BiFeO3/CoFe heterojunctions and a comprehensive theoretical model for their magnetoelectric behavior.

Findings

The response time of CoFe is on the order of 100 ps.

J_int is quantified as 0.32 pJ/m.

Switching success rate improves with reduced CoFe thickness and increased aspect ratio.

Abstract

The switching dynamics of a single-domain BiFeO3/CoFe heterojunction is modeled and key parameters such as interface exchange coupling coefficient are extracted from experimental results. The lower limit of the magnetic order response time of CoFe in the BiFeO3/CoFe heterojunction is theoretically quantified to be on to the order of 100 ps. Our results indicate that the switching behavior of CoFe in the BiFeO3/CoFe heterojunction is dominated by the rotation of the Neel vector in BiFeO3 rather than the unidirectional exchange bias at the interface. We also quantify the magnitude of the interface exchange coupling coefficient J_int to be 0.32 pJ/m by comparing our simulation results with the giant magnetoresistance (GMR) curves and the magnetic hysteresis loop in the experiments. To the best of our knowledge, this is the first time that J_int is extracted quantitatively from experiments. Furthermore, we demonstrate that the switching success rate and the thermal stability of the BiFeO3/CoFe heterojunction can be improved by reducing the thickness of CoFe and increasing the length to width aspect ratio of the BiFeO3/CoFe heterojunction. Our theoretical model provides a comprehensive framework to study the magnetoelectric properties and the manipulation of the magnetic order of CoFe in the BiFeO3/CoFe heterojunction.