Co alloy longitudinal thin film media with ultrahigh coercivity

The effect of CoCrTa intermediate layer and postannealing on the magnetic p roperties and microstructure of CoCrPt/Cr thin film media has been investig ated. Through a postdeposition annealing in a vacuum oven, a tremendous inc rease of coercivity up to 6000 Oe was observed for these CoCrPt/CoCrTa/Cr f ilms, in which the thickness of CoCrTa intermediate layer is about 2.6 mm. X-ray diffraction results showed that the hexagonal-close-packed crystallog raphic structure for the cobalt alloy did not show any change for the sampl e after postannealing. In-plane transmission electron microscope images for the CoCrPt/CoCrTa/Cr films showed no change of the morphology before and a fter annealing and about 15% increase of the grain size for the films after annealing. Delta M curves and remanent squareness results showed that inte rgrain diffusion may result in this improvement of magnetic properties. Ato mic force microscope images showed that the surface roughness for the sampl e after annealing was almost the same as that before annealing. After tailo ring the thickness of the magnetic layer to 10 nm, the coercivity as high a s 5200 Oe and M(r)t value as low as 0.24 memu/cm(2) were obtained, which ma y support ultrahigh bit density than current media. (C) 2000 American Insti tute of Physics. [S0021-8979(00)45708-7].