Magnetic hard disk storage devices are found at the heart of many of the high technology systems we take for granted in modern life.  As essential components of devices such as computers, modern video storage devices and mp3 players, they permeate much of our business and leisure activities and are thus of enormous commercial importance.

At the heart of every hard disk drive are nanomagnetic thin-film recording media that are a  tour de force of materials' science and technology.  Information is stored in bits comprising approximately 200 ferromagnetic grains each currently around 8 nm in diameter, formed by compositional segregation during sputter deposition from a CoCrPt based alloy.  Due to their obvious market pre-eminence there is a very large body of literature concerned with the characterization and performance characteristics of these materials.  Rather surprisingly, there has been relatively very little investigation of their magnetic properties on the length scale of the grains themselves. This is to some large extent due to the problems of finding appropriate physical probes that can produce quantitative results at these (sub-10 nm) length scales.

Over recent years we have worked in collaboration with several of the world market leaders in magnetic storage technology (Seagate, IBM, Hitachi) to use neutrons to address fundamental questions about the physical and magnetic structure of magnetic recording media. Neutrons are an ideal probe of magnetic structure at these length scales. For further information see ILL Scientific Highlight 2006, ILL Scientific Highlight 2002 and other references below.

References

Mapping Local Flux Density Distribution in Nanomagnetic Recording Media,
M Wismayer et al, ILL Scientific Highlight (2006).

Micromagnetic simulation of small-angle neutron scattering from magnetic recording media,
F.Y. Ogrin, S . L. Lee et al., J. Appl. Phys. 99 08G912 (2006).

Towards Better Recording Media ,
'Neutrons and Magnetism', ILL Publication, T Thomson, S L Lee, C D Dewhurst, (2004).

Neutron studies of magnetic recording media,
S L Lee, T Thomson Lee et al, Mat. Res. Symp. Proc. 803 GG4.4.1 (2004).

F.Y. Ogrin and S.L. Lee, Physica B  350 229-232 (2004).

M P Wismayer, S L Lee et al, submitted to APL.

SANS data taken on a sample of perpendicular recording media. The inset shows the model corresponding to the black curve fitted to the data.