In-Plane Anisotropy In CoCr(Ta, Pt)/Cr Films Deposited onto Substrates with Controlled Topography
- PDF / 2,159,680 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 82 Downloads / 150 Views
11
D.J. Twisselmann , B.T. Adekor', M. Farhoud2 , Henry I. Smith2 , P.C. Dorsey3 and C.A. Ross'* IDepartment of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (*caross @mit.edu) 2 Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139 3 Komag Inc, 1704 Automation Parkway, San Jose, CA 95131 ABSTRACT In-plane magnetic anisotropy can be induced in Cr-underlayer/Co-alloy thin films by grooves or scratches in the substrate. To quantify this effect, silica substrates have been prepared with large areas of submicron grooves using interferometric lithography. The growth of Cr films and Cr/Coalloy bilayer films on these substrates has been investigated, and in-plane magnetic anisotropy has been observed. INTRODUCTION Magnetic hard disks are commonly made by depositing a Cr underlayer and a Co-alloy magnetic layer onto a substrate made from nickel-phosphorus (NiP)-plated aluminum. The substrate is often roughened by mechanical abrasion to form a set of circumferential grooves or scratches, in order to reduce stiction between the recording head and the disk. The scratches are typically 20-50 nm deep and 100-500 nm apart. The presence of these scratches can create inplane magnetic anisotropy in which the coercivity, squareness and remanence of the magnetic film are higher parallel to the scratches [1-18]. This effect can be significant. For example, the coercivity can be higher by a factor of 1.3-1.5 parallel to the scratches compared to the perpendicular direction. The enhancement of squareness and coercivity parallel to the scratches can be useful, but its origin is not fully understood. It could be due to elongation [1-2] of the magnetic grains, to growth of chains of grains [3] parallel to the scratches, to in-plane strain differences [4-10], to preferential alignment of the cobalt c-axes along the scratches [10-14], or to differences in magnetic interactions between the two in-plane directions [14-16]. One difficulty in analysing how these scratches can create such a large magnetic effect is that hard-disk substrates contain a range of surface features with various heights and surface profiles. This makes it difficult to ascertain which features of the film microstructure contribute to the magnetic anisotropy. The object of this research is to deposit magnetic films onto substrates with controlled topographic features in order to quantify the variation of the magnetic film properties as a function of surface profile, peak-to-valley height and spatial frequency. To measure magnetic properties such as hysteresis loops or magnetic anisotropy, relatively large areas of thin film are required, of the order of 0.5 cm 2 . These areas need to be patterned with uniform features on a 100-200 nm scale. To pattern an area of this size using electron-beam lithography would be prohibitively slow and expensive. However, interferometric lithography provides a rapid, economical method of patterning wafer-sized areas with periodi
Data Loading...
