Self-Diffusion of Iron in L10 FePd film - as revealed by reflectometric methods

TL;DR

This study investigates the atomic self-diffusion of iron in L10 FePd films using neutron and synchrotron Mössbauer reflectometry, revealing diffusion parameters critical for understanding magnetic storage materials.

Contribution

It provides the first detailed measurement of activation energies and preexponential factors for iron self-diffusion in L10 FePd using non-destructive reflectometry methods.

Findings

Highest activation energy (1.82 eV) in ordered L10 FePd

Lowest activation energy (1.48 eV) in iron-rich regions

Diffusion parameters vary significantly between ordered and iron-rich areas

Abstract

L10 (CuAu(I)-type) ordered FePd as well as FePt and CoPt, due to their high magnetic anisotropy, are candidate materials for future ultra-high density magnetic recording. Atomic diffusion governs the structural relaxation and associated changes in the physical and magnetic properties in these alloys. Such processes involve diffusion paths of a few angstroms. In developing modern storage devices it is indispensable to understand these processes. Neutron reflectometry (NR) and Synchrotron M\"ossbauer Reflectometry (SMR) are suitable non destructive methods to study self-diffusion in a chemically homogenous isotope multilayer with diffusion lengths of the order of a few angstroms. From the diffusion parameters obtained from NR and SMR evaluation we determined activation energies (Q) and preexponent factors (D0) for the distinct environment in the FePd samples. We obtained the highest activation energy (1.82\pm0.38 eV)and lowest preexponential factor((5.76\pm0.35)*10-14 m2/s) for the ordered L10 as oppose to the iron rich regions were the activation energy (1.48\pm0.26 \pmV) found to be lowest and the preexponential factor the highest ((1.01\pm0.61)*10-13 m2/s).