Enhancing the perpendicular magnetic anisotropy of Co–Pt(P) films by epitaxial electrodeposition onto Cu(1 1 1) substrates

Abstract

Co-rich, Co–Pt alloy films containing ∼20 at% Pt and small amounts of P, with thickness from 125 to 1000 nm have been galvanostatically (constant current) grown by electroplating onto Cu seed layers with strong (1 1 1) orientation. The influence of deposition current density (cd=10–50 mA/cm 2) and film thickness on their growth morphology, structural and magnetic properties have been investigated. When electrodeposited on Cu(1 1 1), Co–Pt(P) films develop a microstructure consisting of a disordered hexagonal-closed-packed (hcp) matrix with {0 0 0 1} preferential orientation. At low cd, a small amount of simple cubic L1 2 phase was detected, which disappears altogether by increasing cd to 50 mA/cm 2. The plated films show saturation magnetization in the range 775–832 kA/m (778–832 emu/cm 3), large perpendicular magnetic anisotropy up to 1.02 MJ/m 3 (1.02×10 7 erg/cm 3), and coercivity up to 486 kA/m (6.1 kOe) in the out-of-plane direction. The perpendicular anisotropy was found to originate predominantly from the high magnetocrystalline anisotropy of the hcp phase of Co–Pt(P) with c-axis perpendicular to the substrate.