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 from thickness of an intermediate copper layer in nanosized Fe50Pt50 (15 nm)/Cu (x)/Fe50Pt50 (15 nm) (x = 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 A1(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 A1(FePt) phase forms in all films during deposition. Annealing in vacuum in the temperature range 300–900°C 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 A1(FePt) → L10(FePt) phase transformation raises by 100°C, i.e., to 800°C. Simultaneously, the coercivity in films decreases since Cu dissolves in the FePt lattice.