The current technology of data storage medium in a hard disk drive is a granular magnetic thin film where grain diameters are typically less than 10 nm. Data are written into the medium by a strong, highly confined field produced by a magnetic recording head which set the magnetisation of ~100 grains to form a bit. In order to keep pace with the demand for increased data storage density, the magnetic bit size must be decreased with a commensurate decrease in the grain size to maintain a low noise in the read signal given by the number of grains per bit. However, as individual grain volumes shrink, thermal activition can lead to unintended reversal of magnetisation since thermal energy (kbT) becomes competitive with the grain anisotropy energy (KuV). This is the superparamagnetic effect and it defines the grain volume for a given magnetic material below which the recorded data can be lost due to thermal fluctuations. The magnetic storage industry is therefore seeking a way to delay the onset of the superparamagnetism.

One solution to delay the apprearance of superparamagnetism is to record the information in bit patterned media (BPM). A BPM consists of arrays of nanoscale magnetic islands where each bit of information is stored in an individual island, thus the entire bit volume defines the anisotropy energy rather than the volume of individual grains. Here we demonstrated that extreme Ultra-violet interference lithography (EUV-IL) has particular advantages for the fabrication of BPM due to the possibility to create the high resolution structures over large areas with a high throughput. We are now able to produce magnetic dot arrays with periods down to 35 nm or even less with perpendicular anisotropy magnetic media materials and transmission x-ray microscopy is the ideal technique to study these systems due to the high spatial resolution (15 nm), the sensitivity to perpendicular magnetic domain structures, and the possibility of carrying out measurements in a large, perpendicular applied magnetic field.