Phase separation and dynamic patterning inCu1−xCoxfilms under ion irradiation

Abstract

Phase separation behavior in thin ${\mathrm{Cu}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}$ films under irradiation ($1.8\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ ${\mathrm{Kr}}^{+}$ ions) at different temperatures has been systematically studied for $0.10\ensuremath{\leqslant}x\ensuremath{\leqslant}0.20$. The development of phase separation in irradiated films (estimates of the average size of Co precipitates and concentration of Co in solution) was monitored using magnetic measurements. Analysis of magnetization data in the framework of superparamagnetic theory has shown that at irradiation temperatures $T\ensuremath{\leqslant}330\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, phase separation in $\mathrm{Cu}--\mathrm{Co}$ films of all compositions stabilizes at high doses $(\ensuremath{\approx}1\ifmmode\times\else\texttimes\fi{}{10}^{16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2})$, indicating the existence of temperature-dependent dynamic steady states. At temperatures higher than $\ensuremath{\approx}350\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, indications of thermodynamic-like coarsening are observed. Below $\ensuremath{\approx}300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ FC/ZFC (field-cooled/zero-field cooled) measurements clearly show the randomizing effect of irradiation. The observed phase separation behavior of $\mathrm{Cu}--\mathrm{Co}$ system under irradiation agrees qualitatively well with kinetic Monte Carlo simulations performed in this work and with theoretical predictions of phase evolution in irradiated immiscible alloys.