Difference in coercivity between Co/Fe and Fe/Co bilayers.

A study of the deposition order and film thickness dependence on the coercivity of ferromagnetic bilayers, Co/Fe and Fe/Co, is presented (the sign, "," is for indicating glass or Si substrate position). The magnetization of the Co layer is aligned with the in-plane direction during rf sputter deposition. The thickness is controlled in the range of 3-22 nm. Since there exists a strong exchange interaction between the two ferromagnetic layers, the magnetization reversal process occurs cooperatively, Fe/Co shows an isotropic and hard-magnetic behavior, whereas Co/Fe shows an anisotropic and soft-magnetic behavior. A sudden drop of coercivity in Fe/Co observed at the Fe layer thickness below 5 nm is caused by a decrease in the saturation magnetization of the Fe layer. Due to the surface roughness, the bilayer on the glass substrate possesses a higher coercivity than that of the bilayer deposited on the silicon substrate. The magnetization reversal process of the ferromagnetic bilayers is discussed. [ABSTRACT FROM AUTHOR]