Preparation of anisotropic magneticFeNiPt2films on MgO(001): Atomistic mechanisms for the interdiffusion of twoL10phases

Abstract

$\mathrm{L}{1}_{0}$-ordered $\mathrm{Fe}\mathrm{Ni}{\mathrm{Pt}}_{2}(001)$ thin films were prepared by the interdiffusion of FePt(001) and NiPt(001) layers codeposited on MgO(001) substrates by molecular beam epitaxy (MBE). A large uniaxial magnetic anisotropy $({K}_{u}={9.10}^{5}\phantom{\rule{0.3em}{0ex}}\mathrm{J}∕{\mathrm{m}}^{3})$ and a reduced magnetic transition temperature $({T}_{c}=400\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ were obtained. Growth at $700\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and a first annealing at $800\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ result in a large long-range order parameter reflecting the concentration modulation along the growth direction. This high long-range order parameter is conserved in the $\mathrm{Fe}\mathrm{Ni}{\mathrm{Pt}}_{2}$ layers after interdiffusion at $900\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, contrary to what is expected from a simple vacancy migration process. This experimental observation can be explained either by a 6-jump cycle mechanism or by the alternate diffusion of a double vacancy, which are both favored energetically over a second-nearest-neighbor jump mechanism or the simultaneous diffusion of a double vacancy as shown by quenched molecular dynamics simulations.