Figure 1

Mössbauer spectra of “layer-by-layer” deposited FePd (a) and FePt (b) samples, taken before (A) and after (B) irradiation at 623 K by 130 keV He ions (fluence $2\times {10}^{16}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{s}{\mathrm{c}\mathrm{m}}^{-2}$). In both cases, the latter is almost identical to the spectrum of a high temperature (700 K)-codeposited sample (C), whose perpendicular anisotropy corresponds [11] to nearly complete chemical ordering. Lines are fits [15] to hyperfine field distributions. See discussion in text.Reuse & Permissions

Figure 2

Snapshots from KLMC simulation showing vacancy-induced “$L{1}_0$” chemical ordering during He ion irradiation at 550 K of a $\sim 60\mathrm{n}\mathrm{m}$ FePd film sandwiched between a Pd buffer layer and a Pd capping layer. The figures are cuts (2 atomic planes thick) through the simulation cell—for clarity, only Pd atoms are shown (in black). The (001) orientation of the $L{1}_0$ structure is in the $z$ direction. The total number of vacancies introduced into the cell is shown on each snapshot. The initial structure (first snapshot on left) is either random [no SRO (a)] or incorporates the experimentally determined DSRO from Ref. 11 (b). In (a), ordering occurs equally along the three possible variants (horizontal and vertical stripes correspond to the variants along the $z$ and $x$ axes, and checkerboards to the $y$ direction variant). In (b), DSRO favors ordering along the $z$-axis variant perpendicular to the film; practically complete ordering (third snapshot) corresponds to a vacancy input of about $2\times {10}^{15}$ per ${\mathrm{c}\mathrm{m}}^2$, in agreement with the experimental value. See comments in text.Reuse & Permissions