X-Ray Diffraction Studies on Laminated Magnetic Recording Media

Abstract

We have studied a series of laminated thin films by x-ray diffraction to correlate their structural and magnetic properties. Previous works have shown that the signal-to-noise characteristics of laminated magnetic films with non-magnetic interlayers can exceed that of single layer magnetic films. In the case where the magnetic layer is known to have low signal-to-noise performance, the signal has been observed to increase as the number of layers whereas the noise increases as the square root of the number of layers. This yields a net improvement of the signal-to-noise ratio, making the overall film more attractive as a magnetic recording medium. In this paper, we investigate films which are laminated layers of magnetic CoPtCr and non-magnetic Cr. The films were deposited with sputtering parameters that generally give low noise characteristics in single layer films. Up to four layers of CoPtCr films were made with Cr spacer layers of 2 nm. We observe some improvement in signal-to-noise characteristics and reduction in coercivity. X-ray diffraction analysis shows that the crystallographic c-axis, which corresponds to the magnetic easy axis, becomes more preferentially oriented perpendicular to the film plane with each additional layer. This change in preferred orientation is consistent with the reduced in-plane coercivity of the film. In the double CoPtCr layer with one Cr spacer layer experiment, we see that as the Cr spacer layer is increased from 0.5 to 8 nm, the c-axis of the CoPtCr again becomes more preferentially oriented out of the film plane, resulting in decreased in-plane coercivity. The media signal-to-noise improves once the Cr spacer layer is beyond 2 nm, consistent with previous observations.