In LPI developed functional basis for a weak magnetic field sensors


 Photo source:fian-inform.ru

Employees LPI developed a method of creating ultra-low magnetic field sensors. The functional basis of such sensors can be magnetic structures, which are multi-layered system of alternating layers of different magnetic materials nanoostrovkovyh. Such systems are extremely sensitive to the effects of ultra-low magnetic fields and are able to detect the size of the field to minus 10 in the sixth! degree Oe.

Magnetic structure in question consist of multiple pairs of alternating layers nanoostrovkovyh while nanoislands layers made of different magnetic materials, which differ, for example, the magnitude of the magnetization reversal field. Each such structure is protected above and below the dielectric layer, but each layer may nanoostrova contact with those that lie above or below, and magnetically interact with each other. If so composed layered nanostructure affect even a weak magnetic field, its electrical resistance changes. This phenomenon is called magnitorezestivnym effect on it, and the proposed principle is based detection of magnetic fields.

"We turn first one is sprayed layer of one magnet, then another layer of another magnet, then again the first and so on. The main thing — to have these magnets differ from each other by some magnetic parameters. For example, a distinction is made between magnetism magnetic materials are those that are remagnetized, that is radically changing the direction of the magnetization in a very weak fields, the order of several oersteds it, such as permalloy. A is magnetically, for example, samarium-cobalt — to peremagnitit it must exert to 20 kErsted"- Explains the principle of manufacturing structures leading researcher of the Lebedev Physical Institute, Doctor of Physical and Mathematical Sciences Fedor Pudonin.

Such films can detect magnetic fields of up to minus 10 in the sixth degree Oe. For comparison — the Earth’s magnetic field of about 0.5 Oe. The mechanism of such a uniquely high sensitivity is determined primarily by the giant size magnitorezestivnogo effect, but also an important role to play here are found in specific layers of the vortex magnetization.

Vortices are usually in some larger particles, say, if you take a few hundred atoms, and out of them a drive. This disc of magnetic material behaves as an ordinary magnet, which has the north and south magnetization is twisted along the disk in the form of a vortex, and the magnetic flux is pushed upward in the center. Thus, the central part of the magnetization — it is called kor — perpendicular to the disk surface. This direction micromagnetism now actively studied and developed, for example, cor can hang up, or maybe down, and if we let one position per unit, and the second — for a zero, then this principle, you can create a logical or storage element. For such vortex systems in their "classical" version uses a fairly complex lithographic techniques. To create nanoostrovkovyh structures used method is easier — RF cathode sputtering. But before that the vortices in nanoostrovah considered here were not observed.

"Our islands are very small, and in fact such vortices should not be. But we have observed a certain feature in our systems, which just could not explain. And suppose that we have a whirlwind of not just a single particle, but is distributed between the islands. And it turned out that, theoretically, it is indeed possible"- Says Fedor Pudonin.

Lebedev Institute of Physics is now exploring the possibility of artificial vortex magnetization guidance and management. But the fact of extreme sensitivity to magnetic fields can already be used. The need for sensors weak magnetic fields is very large — to search for minerals in geology, navigation (be it sea, space and aviation) in astrophysics, medicine and biology.

"Overview that these nanostructures are relatively easy to manufacture, — Says another member of the project, a senior researcher, Ph.D. in Physics and Mathematics Anatoly Boltaev, — plus can be operated in an alternating magnetic field and have a high resistivity, so should not overheat and consume high power. This is a great application capabilities. In the first place, of course, medicine — magnetoencephalography, magnetic resonance imaging, magnitogastrografiya, Magnetocardiography. Also, our system can be used in space, since they are radiation resistant, and cosmic radiation on their properties almost no effect. Or, for example, sensors, magnetic fields are used in targeting of submarines — you can track the magnetic relief of the Earth and go with his direction. Use a lot of options. "

Currently, as the most sensitive magnetometers are widely used result, the superconducting quantum interferometers — SQUIDs, which must be cooled to a level of hydrogen or helium temperatures. So to replace SQUID device similar sensitivity to the magnetic field, but does not require a specific process conditions as in the manufacturing and in the work, would come in very handy.

/ 13.10.2011 / On materials ANI "LPI-Inform"

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