Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Unexpectedly Long-Range Effects in Advanced Magnetic Devices

03.07.2009
A tiny grid pattern has led materials scientists at the National Institute of Standards and Technology (NIST) and the Institute of Solid State Physics in Russia to an unexpected finding—the surprisingly strong and long-range effects of certain electromagnetic nanostructures used in data storage.

Their recently reported findings* may add new scientific challenges to the design and manufacture of future ultra-high density data storage devices.

The team was studying the behavior of nanoscale structures that sandwich thin layers of materials with differing magnetic properties. In the past few decades such structures have been the subjects of intense research because they can have unusual and valuable magnetic properties. The data read heads on modern high-density disk drives usually exploit a version of the giant magnetoresistance (GMR) effect, which uses such layered structures for extremely sensitive magnetic field detectors.

Arrays of nanoscale sandwiches of a similar type might be used in future data storage devices that would outdo even today’s astonishingly capacious microdrives because in principle the structures could be made even smaller than the minimum practical size for the magnetic islands that record data on hard disk drives, according to NIST metallurgist Robert Shull.

The key trick is to cover a thin layer of a ferromagnetic material, in which the magnetic direction of electrons, or “spins,” tend to order themselves in the same direction, with an antiferromagnetic layer in which the spins tend to orient in opposite directions. By itself, the ferromagnetic layer will tend to magnetize in the direction of an externally imposed magnetic field—and just as easily magnetize in the opposite direction if the external field is reversed.

For reasons that are still debated, the presence of the antiferromagnetic layer changes this. It biases the ferromagnet in one preferred direction, essentially pinning its field in that orientation. In a magnetoresistance read head, for example, this pinned layer serves as a reference direction that the sensor uses in detecting changing field directions on the disk that it is “reading.”.

Researchers have long understood this pinning effect to be a short-range phenomenon. The influence of the antiferromagnetic layer is felt only a few tens of nanometers down into the ferromagnetic layer—verticallly. But what about sideways? To find out, the NIST/ISSP team started with a thin ferromagnetic film covering a silicon wafer and then added on top a grid of antiferromagnetic strips about 10 nanometers thick and 10 micrometers wide, separated by gaps of about 100 micrometers. Using an instrument that provided real-time images of the magnetization within grid the structure, the team watched the grid structure as they increased and decreased the magnetic field surrounding it.

What they found surprised them.

As expected, the ferromagnetic material directly under the grid lines showed the pinning effect, but, quite unexpectedly, so did the uncovered material in regions between the grid lines far removed from the antiferromagnetic material. “This pinning effect extends for maybe tens of nanometers down into the ferromagnet right underneath,” explains Shull, “so you might expect that there could be some residual effect maybe tens of nanometers away from it to the sides. But you wouldn’t expect it to extend 10 micrometers away—that’s 10 thousand nanometers.” In fact, the effect extends to regions 50 micrometers away from the closest antiferromagnetic strip, at least 1,000 times further than was previously known to be possible.

The ramifications, says Shull, are that engineers planning to build dense arrays of these structures onto a chip for high-performance memory or sensor devices will find interesting new scientific issues for investigation in optimizing how closely they can be packed without interfering with each other.

* Y.P. Kabanov, V.I. Nikitenko, O.A. Tikhomirov, W.F. Egelhoff, A.J. Shapiro and R.D. Shull. Unexpectedly long-range influence on thin-film magnetization reversal of a ferromagnet by a rectangular array of FeMn pinning films. Physical Review B 79, 144435, 2009. DOI: 10.1103/PhysRevB.79.144435.

Michael Baum | Newswise Science News
Further information:
http://www.nist.gov

More articles from Physics and Astronomy:

nachricht A chip for environmental and health monitoring
15.12.2017 | Friedrich-Alexander-Universität Erlangen-Nürnberg

nachricht New type of smart windows use liquid to switch from clear to reflective
14.12.2017 | The Optical Society

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Plasmonic biosensors enable development of new easy-to-use health tests

14.12.2017 | Health and Medicine

New type of smart windows use liquid to switch from clear to reflective

14.12.2017 | Physics and Astronomy

BigH1 -- The key histone for male fertility

14.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>