Effect of Copper on the Formation of Ordered L1₀(FePt) Phase in Nanosized Fe₅₀Pt₅₀/Cu/Fe₅₀Pt₅₀ Films on SiO₂/Si(001) Substrates

Abstract

The effect of Cu intermediate layer thickness in nanosized Fe₅₀Pt₅₀ (15 nm) / Cu (x) / Fe₅₀Pt₅₀ (15 nm) (where х = 7.5, 15, and 30 nm) composite films on SiO₂ (100 nm) / Si(001) substrates on the diffusion-controlled phase formation processes—transformation of the disordered magnetically soft А1(FePt) phase into the ordered magnetically hard L1₀(FePt) phase during annealing in vacuum—is studied by physical materials science methods: X-ray diffraction and measurement of magnetic properties. The Аl(FePt) phase forms in all films during deposition. Annealing in vacuum in the temperature range 300–900 ºС is accompanied by thermally activated diffusion processes between the Cu and FePt layers. When thickness of the intermediate Cu layer increases from 7.5 nm up to 15 nm, the onset temperature of Аl(FePt)→ L1₀(FePt) phase transformation raises by 100 °С, i.e., tо 800 °С. Simultaneously, the coercivity in films decreases since Cu dissolves in the FePt lattice.