Comparison of bit-patterned media fabricated by methods of direct deposition and ion-milling of cobalt/palladium multilayers

Abstract

In the fabrication of bit-patterned media (BPM), two processes are commonly used, i.e., the pattern transfer by ion-milling into an underlying film of magnetic material, and the direct deposition of the magnetic material onto a pre-patterned substrate. We experimentally compared the switching performance of the BPM based on Co/Pd multilayers fabricated using these methods in terms of their switching field distribution (SFD) and physical characteristics of the bits. Our results show that both methods resulted in a narrow (∼15%) SFD at low areal recording densities of ∼0.15 Tdot/in2. However, at higher densities of up to 0.6 Tdot/in2, the SFD of the ion-milled samples detrimentally broadened to ∼30% while the BPM from the direct-deposition method maintained its narrow SFD up to a high bit density of 0.6 Tdot/in2. Our results suggest that in Co/Pd multilayer systems, the direct-deposition method, which produces more uniform bit sizes and profiles especially at high bit densities, is a more promising approach to achieving high-density BPM.