Improvement of magnetocrystalline anisotropy of columnar structure for epitaxially grown CoCr-based perpendicular media

Abstract

To improve uniaxial magnetic anisotropy Kugrain of c-plane-oriented columnar grains for CoCr-based perpendicular recording media, an epitaxial growth technique has been applied. The main results are as follows. (1) Using a Ru(3 nm) or Co60Cr40(20 nm)/C(1 nm) intermediate layer, Kugrain for a Co69Cr19Pt8B4 medium was enhanced from 2.04×106 erg/cm3 to 2.53×106 erg/cm3 or to 2.76×106 erg/cm3, respectively. (2) The enhancement of Kugrain depends on the composition of the magnetic layer when using the Co60Cr40/C intermediate layer. (3) The epitaxial growth technique is also effective to increase KugrainVact/kT. Especially, in the media with a high concentration of B or Cr, the thermal stability is improved mainly due to an increase of Kugrain rather than an enlargement of Vact.

Magnetization states and magnetization processes in nanostructures: From a single layer to multilayers

“…Several mechanisms were considered to determine the origin of the PMA in layered films . These are: (i) single axis magneto crystalline anisotropy (e.g., hexagonal Co or well‐ordered appropriately oriented L1 0 phase of FePt ), stress‐induced anisotropy (e.g., CoCrPt , Au/Co/Au , Co/Ni ), Néel surface anisotropy (e.g., Au/Co , Co/Ni , MgO/CoFeB , MgO/Fe ), exchange anisotropy (e.g., CoO/CoPt multilayer ), pair ordering (e.g., RE‐TM amorphous films) , single ion anisotropy (e.g., RE‐TM multilayers ), bond‐orientation anisotropy (e.g., RE‐TM amorphous films ), and shape anisotropy (e.g., CoCr films with columnar structure ). Only the last mentioned mechanism is related to the dipolar interaction.…”