The exact time of the exchange interaction of atoms of a ferromagnetic alloy is revealed.
Using lasers, physicists from two scientific institutions – the National Institute of Standards and Technology and the University of Colorado at Boulder – have obtained some research results that in the future could help create information storage devices with a denser structure of memory cells and faster performance.
During the experiments, a femtosecond laser was used, which worked in the ultraviolet range using high harmonic generation technology. At the same time, some changes were noticed in the magnetic properties in the atoms of nickel and iron, which are part of the ferromagnetic alloy (a special alloy, permalloy, took part in the experiment).
Most sources of information storage (hard drives) in the future will look like magnetic drives, in which the magnetization and demagnetization of elements occurs due to the action of lasers with an ultrahigh pulse.
The very phenomenon of ultrafast demagnetization when exposed to femtosecond lasers was discovered back in 1996. However, it was then believed that the phenomenon of demagnetization occurs in the material uniformly for each atom in the structure of the ferroalloy. This should be assumed based on the data available regarding the processes occurring at normal speed. The interaction of atoms in a material under normal conditions is reduced to the fact that the electromagnetic properties of each particle change at the same rate. Experiments carried out recently have shown that in the processes that occur during pico – and femtosecond time intervals, the situation is quite different. One gets the impression that the process of exchange interaction of atoms simply does not have time to exert such an effect on nickel atoms in the iron-nickel alloy. For this reason, the phenomenon of demagnetization in iron atoms occurs faster than in nickel.
Despite the fact that after a few quadrillionths of a second, the nickel and iron atoms still synchronize their magnetization in the ferroalloy, the gap at shorter time intervals makes it possible to think about the possibility of a quick creation of the newest hard drives, in which the processes of magnetization and demagnetization can occur even faster than originally intended.
In theory, the readout speed will be limited only by the frequency of operating ultrashort laser pulses. In other words, the frequency can drop to 5 femtoseconds, which is about 200 trillion. vibrations per second. The time difference in the magnetization of nickel and iron opens up the prospect of creating data carriers in which it will be possible to place 1 bit of information on one single atom.