Abstract
Cobalt-platinum alloy films have long been attractive as materials for permanent magnets due to their high magnetic anisotropy, high coercivity, and good corrosion resistance. Of continuing interests are the magnetization reversal mechanism and coercivity of such films for high-density magnetic recording media. In this article, Pt_3Co alloy films are produced using a sputtering system. To understand the reversal mechanism of Pt_3Co alloy films, the recoil loops from the major hysteresis loop have been measured. The reversible magnetization M_<rev> dependence of the irreversible magnetization M_<irr> exhibits a minimum when M_<irr> is slightly larger than zero, which is the characteristic of a material that contains domain walls bowing during reversal caused by localized pinning due to dipolar fields for the films. By analyzing the linear dependence of the coercivity on the anisotropy field at different temperatures, the strength of the local dipolar fields N_<eff> which jnfluences the creation of the reversed magnetic nucleus, is estimated. We found a positive value of N_<eff> which indicates that reversal process is mainly controlled by pinning due to local dipolar fields. It is also supposed that the dipolar fields originated from irregular local random anisotropy caused by residual stress, cavities, or inclusions, may be effective sources of pinning in the reversal process, and may strongly affect the coercivity of the film.
