We have studied the variation of perpendicular magnetic anisotropy (PMA) of CoFeB layers with the oxidation degree of the MgO buffer layers. After annealing at 330 °C, the out-of-plane anisotropy field (Hk) of 1.5-nm CoFeB could be optimized to 3.1 kOe. To investigate the orbital hybridization of the Fe-3d and O-2p, the orbital moments per hole (morb/Nh) of Fe in annealed CoFeB layers were extracted by using x-ray magnetic circular dichroism. The dependence of morb/Nh on the oxidation time of MgO coincided with that of Hk, which revealed that PMA of annealed CoFeB originated from the interfacial orbital hybridization.

We study exchange coupled composite (ECC) media where both the hard and soft coupled layers possess perpendicular anisotropy or one of the layers is superparamagnetic. Our model is used to demonstrate the effect of the dipolar interactions on the coercive field. A series of ECC samples with various thicknesses of Ru spacer is manufactured and analyzed. The structure of the samples prepared is CoPtCr-SiO2∕Ru∕CoPtCr-SiO2, with the composition varied around that of (CoPt17Cr10)90-(SiO2)10. The acquired experimental data are used to illustrate the significance of magnetostatic interactions between the two coupled magnetic layers.

We demonstrate using both structural and magnetic analyses that an antiferromagnetic MnRu intermediate layer can simultaneously increase the anisotropy constant and reduce the intergranular exchange coupling of a CoPtCr-SiO 2 recording layer. The anisotropy constant of CoPtCr-SiO 2 is increased by an exchange coupling with the adjacent antiferromagnetic MnRu intermediate layer. Additionally, the MnRu layer leads to better SiO 2 segregation within the recording layer which then weakens intergrain exchange coupling. While the enhanced grain isolation leads to a reduction in the activation volume, a potential loss in thermal stability is avoided due to the enhanced anisotropy.

(001)-oriented FePt graded media are obtained by using PtMn underlayers. The PtMn underlayer not only behaves as the (001) structural template but provides the diffusion source of Mn. The diffusion of Mn into FePt reduces its anisotropy but, on the other hand, the exchange coupling between antiferromagnetic PtMn and ferromagnetic FePt enhances the anisotropy. Hysteresis loops taken from x-ray magnetic circular dichroism confirm the competition between these two effects, leading to the lowest anisotropy in the middle of FePt.

The laminated soft layer (LSL) [Pt/CoPtCr-SiO2]5 was used in exchange coupled composite (ECC) media and exhibited a tunable perpendicular anisotropy by changing the thickness of Pt. By using x-ray magnetic circular dichroism, the incoherent reversal in the ECC media with a LSL was directly observed. The nucleation field of ECC media was found to be dominated by the anisotropy of the LSL. The increased thickness of the Pt layers in the LSL reduced the anisotropy, which promoted incoherent reversal; however, with the Pt thickness increasing larger than 0.9 nm, the interlayer coupling between the LSL and the hard layer was significantly reduced, and thus the assisting effect was suppressed. Furthermore, the dependence of remanent coercivity Hcr on the Pt thickness confirmed that the assisting effect can be optimized by controlling the Pt thickness to balance the LSL anisotropy and the interlayer coupling.