Polarized neutron reflectometry study of Fe16N2 with Giant Saturation Magnetization prepared by N Inter-diffusion in Annealed Fe-N Thin Films

TL;DR

This study demonstrates a novel synthesis method for Fe16N2 thin films with giant saturation magnetization up to 2360 emu/cm3, surpassing known limits, using N inter-diffusion and annealing techniques.

Contribution

It introduces a new annealing process that enables the growth of Fe16N2 with unprecedented magnetization levels in thin films.

Findings

Achieved a saturation magnetization of 2360 emu/cm3.

Demonstrated N inter-diffusion as a key process.

Potential application in magnetic recording materials.

Abstract

We report a synthesis route to grow iron nitride thin films with giant saturation magnetization (Ms) through an N inter-diffusion process. By post annealing Fe/Fe-N structured films grown on GaAs(001) substrates, nitrogen diffuses from the over-doped amorphous-like Fe-N layer into strained crystalline Fe layer and facilitates the development of metastable Fe16N2 phase. As explored by polarized neutron reflectometry, the depth-dependent Ms profile can be well described by a model with the presence of a giant Ms up to 2360 emu/cm3 at near-substrate interface, corresponding to the strained regions of these annealed films. This is much larger than the currently known limit (Fe65Co35 with Ms \sim 1900 emu/cm3). The present synthesis method can be used to develop writer materials for future magnetic recording application.