Abstract
Lower noise and higher thermal stability are two main key points in the process of achieving high areal density recording. The method of promoting SNR includes increasing the number of grain per bit to increase intensity of signal and decreasing Mrt to decrease noise. Both two methods improved SNR in the opinion of reducing energy barrier KuV and would reduced the ability to resist agitation from thermal energy and leaved the moments unstable. Antiferromagnetically coupled media was proposed in 1999 as a pathway for extending high-density longitudinal recording media while maintaining thermal stability. The important advantages of AFC media are: high signal resolution due to smaller Mrt and higher thermal stability due to larger grain volume.I have investigated that the interlayer exchange coupling constant J and exchange field are enhanced by conventional AFC media with Co interlayer on each side of Ru. But the Hc of upper layers decreases and Hc of lower layers increases with tCo, which is opposite to the useful properties of AFC media. To prevent the increase of Hc,LL due to inserting Co layer, I develop another different design of advanced AFC media structure. In the new structure, I retain the interlayer Co on the bottom side of Ru and insert a nonmagnetic layer such as Ru or CoCr with low content of Co into the interface of LL/Co to isolate interaction between Co interlayer and lower layer. Advantages of inserting NM layer into double stabilizing layers are as follows：higher interlayer exchange coupling, easier switching of lower layers, and lower net Mrt.