AlN: A Hexagonal-Nitride Seed Layer Underneath Ru for Granular-Type Perpendicular Magnetic Recording Media

A new hexagonal-nitride material, AlN, is proposed in place of current metallic materials as a seed layer underneath the Ru layer for perpendicular recording media. It was found that (1) c-plane oriented AlN with wurtzite structure can be realized by direct current reactive sputtering, (2) c axis direction distribution (FWHM) of AlN decreases with the change in buffer structure from nano-crystalline to amorphous, which also results in reduction of the FWHM of Ru, (3) a Ru layer with low averaged grain size less than 8.0 nm retains low FWHM at less than 4.0^deg , and surface roughness with peak to valley of 2.0 nm is available by insertion of the AlN seed layer, (4) for substrate/FeCoB buffer (10 nm)/AlN/Ru/CoPtCr-SiO₂ (16 nm) media, an increase in the thickness of the AlN layer is also effective for magnetic isolation of granular-type media, in addition to a decrease in the Ru layer thickness, which means that the AlN layer can substitute a part of the Ru layer.