Thermal stability and nanostructure of CoCrPt longitudinal recording media

Authors

Mingjun Yu, University of Nebraska - Lincoln
Mary F. Doerner, IBM Storage Systems Division, San Jose, CA
David J. Sellmyer, University of Nebraska-LincolnFollow

Date of this Version

July 1998

Comments

Published by IEEE; IEEE Trans. Mag. 34, 1534 (1998). ©1998 IEEE. Permission to use. http://ieeexplore.ieee.org/

Abstract

We report a systematic study of activation volumes and their correlation with physical grain sizes and thermal stability in CoCrPt media fabricated by magnetron sputtering. Different underlayers and CoCrPt layer thicknesses were used to provide a range of lateral grain sizes, M_Iδ (product of remanence M_I and film thickness δ) values, and remanence coercivities. Two methods, namely the field-sweep-rate dependence of coercivity and measurements of magnetic viscosity and irreversible susceptibility, were used to determine the activation volumes and the results obtained from the two methods are in reasonable agreement. For CoCrPt layer thickness from 10 nm to 27 nm, the activation volumes of these films range from about 3x10^-18 cm³ to 5X IO^-18 cm ³, which indicate that these films are thermally stable. Furthermore, for most samples the activation volumes are close to the volumes of the physical CoCrPt grains. This suggests that the magnetic grains in these films switch almost independently. Films with physical grain sizes small enough to approach thermal instability are also discussed.