Magnetic Structure in Fe/Sm-Co Exchange Spring Bilayers with Intermixed Interfaces

TL;DR

This study combines polarized neutron reflectometry and micromagnetic simulations to analyze the magnetic properties of Fe/Sm-Co bilayers, revealing an intermixed interface that enhances exchange coupling but reduces overall magnetization.

Contribution

It provides detailed characterization of the interfacial magnetic profile in Fe/Sm-Co bilayers, highlighting the effects of intermixing on magnetic properties and exchange coupling.

Findings

Interfacial region extends about 8 nm with gradual property changes.

Intermixed interface improves exchange coupling between layers.

Magnetization is reduced in the intermixed region.

Abstract

The depth profile of the intrinsic magnetic properties in an Fe/Sm-Co bilayer fabricated under nearly optimal spring-magnet conditions was determined by complementary studies of polarized neutron reflectometry and micromagnetic simulations. We found that at the Fe/Sm-Co interface the magnetic properties change gradually at the length scale of 8 nm. In this intermixed interfacial region, the saturation magnetization and magnetic anisotropy are lower and the exchange stiffness is higher than values estimated from the model based on a mixture of Fe and Sm-Co phases. Therefore, the intermixed interface yields superior exchange coupling between the Fe and Sm-Co layers, but at the cost of average magnetization.