Origin of enhanced anisotropy in FePt-C granular films revealed by XMCD

We study the effect of carbon segregants on the spin and orbital moments of L1(0) FePt granular media using x-ray magnetic circular dichroism (XMCD) spectroscopy and report an effective decoupling of the structural film properties from the magnetic parameters of the grains. The carbon concentration reduces the grain size from (200+/-160) nm(2) down to (50+/-20) nm(2) for 40mol. % C and improves sphericity and the order of grains, while preserving the crystalline order, spin and orbital moments, and perpendicular magnetocrystalline anisotropy. We identify the primary cause of enhanced saturation and coercive fields as the reduced demagnetization fields of individual grains. The ability to shrink grains without impairing their magnetic properties is a critical requirement for the commercialization of Heat-Assisted Magnetic Recording. Published under license by AIP Publishing.