The storage capacity of hard drives has grown steadily for decades. Now, she comes up against limits that are dictated by the laws of physics. Because the smaller the magnetic bit units, the more unstable it will be, so that the stored information is lost with time. There are already stable magnetic materials. The problem is that magnetic fields in these materials are so stable that they can no longer be switched with the stylus. Techniques such as heat-assisted magnetic recording heat then locally the area around the magnetic information unit (bit), the heat will cause the system so to speak, over the energy barrier, so that the magnetic bits can be switched, after cooling, it is stable again.
Allow laser pulses easy switching an international team has now presented a completely new approach to overcome the energy barrier in a magnetic material. They lower the barrier for magnetic manipulation by causing a phase transition in the material from the insulating to the metallic state. The team, which is headed by Prof. Hiroki Wadati of the University of Tokyo, has the material BaFeO 3 (BFO) studied with ultrashort X-ray pulses at Femtospex measuring station of the photon source BESSY II of HZB.BFO is a ferromagnetic insulator with stable magnetic order. But when one bombards the material with laser pulses above a certain threshold power, can be easily manipulated at once the magnetic order.
Cause is a local phase transition , the researchers were able to determine the threshold for the magnetic switch and show that it forms a transition state in the material: In the short term the insulator BFO is metallic. Unlike conventional magnetic materials where laser excitation induces a quasi-metallic state for less than a trillionth of a second, the metallic state stabilizes in BFO itself. It is characterized receive about a thousand times longer and therefore is long enough in this time to write as bits with a short magnetic pulse. Thus, the effect for technical applications is interesting.
Ultra-fast process observed at Femtospex measuring station The results now. In Phys Rev. Letters are published, showing a new way to manipulate data. Such a comprehensive picture of ultrafast processes to win in a material was possible because of Femtospex measuring station at BESSY II of HZB, allows to attract magnetic and spectroscopic information in a single experiment.