Elastic properties of γ′-Fe4N probed by nanoindentation and ab initio calculation

We studied the elastic properties of γ′-Fe4N experimentally and theoretically, as the difference between calculated and measured literature data is up to 31%. A phase-pure γ′-Fe4N thin film and a bulk-like sample were synthesized using a reactive magnetron sputtering technique and a two-step ammonolysis reaction, respectively. The elastic moduli were measured to be 157 ± 11 and 159 ± 17 GPa, respectively, by nanoindentation. For nanoindentation on bulk-like γ′-Fe4N, the correction of structural compliance was applied to remove the influence of the porosity as well as of mounting. These measured elastic moduli are consistent with the value of 162 GPa obtained from ab initio calculations.