Nanocomposites and nanomaterials
The L10 FePd ordered phase formation in FePd thin films at annealing in hydrogen atmosphere
P.V. Makushko, M.N. Shamis, T.I. Verbytska, and Yu.N. Makogon
Igor Sikorsky Kyiv Polytechnic Institute, Department of Physics of Metals, Peremogy av. 37, 03056, Kyiv, Ukraine
E-mail: corresponding_author makushko@outlook.com

FePd and FePt based thin films with ordered L10 structure are perspective materials for ultra-high density magnetic recording. Atmosphere during deposition and post-annealing have significant influence on the kinetics of ordering process and development of magnetic properties [1].
The aim of this work was to investigate the influence of annealing atmosphere (vacuum and H2), temperature and duration on the ordering processes and magnetic behavior of Fe50Pd50 thin films. 
Fe50Pd50(5 nm) thin films were prepared by magnetron sputtering at room temperature onto thermally oxidized silicon substrates. As-deposited films with disordered A1 FePd structure were subjected to annealing in vacuum or hydrogen atmosphere at temperatures up to 800 °C to initiate the formation of chemically ordered L10 FePd phase. 
It was established that presence of hydrogen in annealing atmosphere affects diffusion phase formation processes. After annealing in hydrogen atmosphere at 650 °C for 1 h formation of ordered L10 FePd phase was found to be more pronounced compared to annealing in vacuum. Increasing of annealing temperature or duration results in activation of disordering processes. This is due to penetration of hydrogen atoms into the film, which induces additional strain, weakens Fe-Pd interatomic bonds and affects its electronic structure [2]. The last is reflected in development of magnetic properties of thin films: superparamagnetic behavior is observed for disordered state, simultaneously, hard magnetic properties of L10 ordered phase are improved. 

1.	Weller D., Parker G., Mosendz O., Lyberatos A., Mitin D., Safonova N. Y and Albrecht M, Article: FePt heat assisted magnetic recording media // J. Vac. Sci. Technol. B.- 2016.- 34, P. 060801.
2.	Estela A. Gonzalez, Paula V. Jasen, Norberto J. Castellani Juan A. The effect of interstitial hydrogen on the electronic structure of Fe–Pd alloys // J. Phys. Chem. Solids.- 2004.- 65, P. 1799–1807.