Information technology

The development and improvement of materials for the most advanced technologies poses challenges that X-ray FELs can help to solve. Progress in information technology, for example, results from the ability to store information on smaller and smaller areas, and also on the ability to read and write it as rapidly as possible.

Present-day hard disc drives use layered magnetic materials in which the tiny magnetic moment of each grain in the topmost layer can be magnetized in the top or down direction to indicate a “0” or a “1”, thus storing one bit of information. Writing usually takes place by applying magnetic fields, reading occurs by measuring electrical resistance that depends on the orientation of the magnetic moment of the top layer. In recent years it was discovered that a short laser pulse with circularly polarized light, which has two possible directions like a left-turning or right-turning screw, can also write in a sample by changing the magnetic polarity, but more quickly . The European XFEL is going to be equipped with a special device to produce circular polarized X-rays that will permit researchers to obtain a map of the magnetization of a sample and of its evolution in time. This will lead to a better understanding of ultrafast magnetization erasure and re-writing by optical laser pulses and should contribute to establishing the mechanism and approach the physical speed limits of magnetic recording.