CoNiCr/Cr and CoCrTa/Cr films for longitudinal magnetic recording media were deposited on Corning 7059 glass substrate by RF magnetron sputtering at room temperature and 250℃. The thickness of Cr underlayer was varied from 500 to 3000Å and that of magnetic layer was fixed at 700Å. The films deposited at room temperature were annealed in a vacuum chamber. Annealing temperature was varied from 100 to 400℃ and annealing time was varied from 2 to 8 hours.
Coercivity and squareness were measured by using vibrating sample magnetometer. Film morphology and crystalltexture were studied by using scanning electron microscopy and thin film X-ray diffractometer. Auger electron spectroscopy was used to study the depth profile of annealed films.
The Cr film deposited on glass substrate had a columnar structure with (110) prefered orientation. And the CoNiCr film deposited on Cr underlayer had (1010) and (1011) prefered orientation. But the film deposited on glass substrate without Cr underlayer had (0002) prefered orientation. This prefered orientation change might be associated with the epitaxial growth of CoNiCr film on Cr underlayer.
The coercivity of CoNiCr/Cr and CoCrTa/Cr films deposited at room temperature increased as the Cr underlayer thickness increased and then showed a constant value when the Cr underlayer thickness was larger than 2000Å. The squareness decreased slightly with increasing Cr underlayer thickness.
The coercivity of films deposited at 250℃ increased monotonically with increasing Cr underlayer thickness. The squareness decreased slightly with increasing Cr underlayer thickness. The films deposited at 250℃ showed 100 Oe higher coercivity than that of the film deposited at room temperature.
The coercivity of the films annealed in vacuum initially increased with increasing annealing time. But the values were not increased with further increase in annealing time. The difference between the coercivity of not-annealed films and that of annealed films increased with increasing Cr underlayer thickness. No significant change was found in squareness after annealing, regardless of Cr underlayer thickness. The change in magnetic properties of annealed films might be associated with Cr diffusion from Cr underlayer into magnetic layer during annealing.
