Depth profile of spin and orbital magnetic moments in a subnanometer Pt film on Co

Abstract

The magnetic properties of a few atomic Pt layers on a 15-nm-thick Co film were studied by x-ray magnetic circular dichroism spectroscopy at the Pt ${L}_{2,3}$ edges. The spin and orbital magnetic moments of the Pt $5d$ electrons were separated using the sum rules, and the depth profiles of these moments were determined as a function of the distance from the Co-Pt interface. A Pt atom has a total magnetic moment of $0.61\phantom{\rule{0.3em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}∕\text{atom}$ at the interface, and the moment decreases exponentially with the distance from the interface with a characteristic decay length of 0.41 nm. Four atomic Pt layers near the interface possess 90% of the total magnetization of Pt. The Pt orbital magnetic moment is more than 15% relative to the spin moment and confined to two atomic layers near the interface. The orbital moment was found to be isotropic in the dichroism measurements using external magnetic fields perpendicular and parallel to the film plane. These properties of Pt magnetization are discussed in the context of thermal stability of magnetic recording media covered with a thin Pt overlayer.