Perpendicular magnetic anisotropy and magnetostriction of sputtered Co/Pd and Co/Pt multilayered films

Abstract

Magnetic properties of Co/Pd and Co/Pt multilayers were studied as a function of sputtering gas pressure. It was found that the magnetic properties of the films depended upon the sputtering gas pressure, and large coercivity (several kOe) and a perfect squareness of the perpendicular hysteresis loop were attained by the deposition at the high gas pressure. These multilayers are suitable for perpendicular magnetic recording media. In the Co/Pd, the origin of the perpendicular magnetic anisotropy is mainly an interfacial anisotropy, although there exists a stress-induced anisotropy for the films with the relatively short periodicity. The perpendicular magnetic anisotropy of the Co/Pt can be concerned with the Co-Pt mixture formed at the interface of the multilayer structure. The magnetostriction of the Co/Pd films with the relatively short periodicity is extraordinarily large with a negative sign, since Co atoms adjacent to Pd atoms at the interface could induce larger magnetostriction than that of pure Co. As the periodicity increased, the magnetostriction became small, but the sign remained negative. For the films with the long periodicity the magnetostriction may be caused by pure Co of the layer interior. On the contrary, the Co/Pt films have a positive magnetostriction even for the thick Co layers. The data indicate existence of the Co-Pt mixture at the interface.