Effect of Magnetic CoZrNb Seed Layers on Pd/Co Multilayers
- PDF / 1,378,753 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 52 Downloads / 189 Views
Introduction Use of a single-pole recording transducer in perpendicular recording necessitates a flux return path under the storage medium [1]. One way to produce such a flux return path is by deposition of a soft magnetic underlayer before the media layer. In this case, the flux return path can also be used as a crystallographic and microstructural seed layer for the medium, allowing one to incorporate desirable features. For Pd/Co multilayer recording media, the desired features include a very small magnetic domain size and a strong net perpendicular anisotropy energy [2]. Growth of a grain structure of this type can be enhanced by a nanocrystalline seed layer. In principle, small, well-textured grains can be attained by seeding the multilayer with a nanocrystalline phase which could lead to an increase in recording density. A CoZrNb (CZN) alloy was chosen to be the seed layer for Pd/Co multilayers for perpendicular magnetic recording since CZN a soft magnetic material, and it can be deposited as a nanocrystalline or amorphous phase [3,4].
161 Mat. Res. Soc. Symp. Proc. Vol. 382 ©1995 Materials Research Society
Experimental Multilayers and seed layers were grown in a high vacuum deposition system equipped with a 14" cryopump and three 1.3" magnetron sputter deposition sources. Substrates were baked in vacuum at 100°C prior to deposition to remove environmental deposits. Pd was DC sputtered at a power of 20W, Co was DC sputtered at 20W, and CZN was DC sputtered at 30W. Pd/Co multilayers were grown on single crystal silicon substrates coated with 500A of amorphous silicon nitride. Polycrystalline CZN seed layers were deposited prior to the multilayers to seed grain growth in the multilayer. A series of samples were grown, consisting of 20x(Pd(11 k)/Co(4k)) grown on top of CZN layers ranging in thickness from zero to 660 '. Since these gave evidence of exchange coupling between the multilayer and the CZN seed, an additional sample was prepared by depositing a 50A Pd isolation layer between the CZN seed layer and the Pd/Co multilayers. Results and Discussion Figure 1 (a - e) shows out-of-plane Pd/Co multilayer hysteresis loops for multilayer films deposited on CZN seed layers of various thicknesses. The measured hysteresis loops were a superposition of the loops from the media and the soft underlayer, e.g. they were sheared by the 4itMs contribution of the CZN layer. This contribution has been subtracted from the loops shown in the figure. Figure 1(a) shows the hysteresis loop for a multilayer deposited directly on the silicon nitride layer. The loop is square and has a high coercivity. A 55k CZN seed layer causes a marked change in the magnetic characteristics of the multilayer. This is a result of exchange coupling between the CZN layer and the multilayer, which reduces the nucleation field and thus the coercivity. The hysteresis loop remains square for this CZN thickness. Between CZN layer thicknesses of 55A to 660A (Fig. 1 b - e), the shearing of the loops increases. The coercivity is controlled by both the nu
Data Loading...
