New Effect During Laser Induced Switching of Bits for Higher Storage Densities

An international team has discovered at BESSY II a new way how the information density can be increased further in future storage media. They fired for the ferromagnetic material BaFeO 3 (BFO) with short laser pulses, which cause a momentary phase transition in the material. This made ​​it possible to switch otherwise stable magnetic regions very locally. This they were able to prove with ultrashort X-ray pulses at the Femtospex plant. This effect could provide a new way to store data. The results are now in Phys. Rev. Letters published.

storage densities
BFO has a perovskite crystal structure. Image: University of Tokyo

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.