The formation of nanosized hard magnetic FePt films alloyed by Ag, Au, Cu for increase of magnetic recording density

підвищення щільності магнітного запису

New principles of stable nanoscale hard magnetic FePt films formation with ordered L10(FePt) phase are created by the way of regulation the rate of solid state reactions by using additional layers of alloying elements (Ag, Au, Cu) as regulators of diffusion flows. It is reached the decrease of the hard magnetic L10(FePt) phase formation temperature on 100 K due to extra driving force at the creation of additional interfaces and stress state that accelerate the diffusion processes of ordering. The reduction of magnetic interaction between grains and, consequently, increase in the coercivity is achieved by introducing of intermediate Ag, or Au layers, which are insoluble in Fe50Pt50 films. It is proposed a new scientific approach the use at heat treatment instead of vacuum the Ar with 3 vol. % H2 atmosphere that allows to neutralize of oxidation. The implementation of the hydrogen atoms in L10(FePt) phase lattice causes the formation of solid solutions, providing thermal stabilization of grain size L10(FePt) phase near 20 nm and a surface roughness minimization of film material at ± 2 nm.

First obtained by increasing the compressive stresses level in the film on single crystalline Al2O3(0001) substrates the [001] orientation grain growth of L10(FePt) phase grains with a c-axis of easy magnetization perpendicular to the substrate. It is created and experimental confirmed the model that the formation of a homogeneous FePt layer in Pt/Fe and Pt/Ag/Fe films on SiO2/Si(001) going through transformations induced by grain boundary diffusion, and the homogeneous layer formed through movement of grain boundaries in directions perpendicular to their original positions.

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