October 13th, 2007
Ferrotoroidicity, key to faster hard disks?
I bet that not many of you have heard about ferrotoroidicity. In fact, Google returns only 37 results about this concept as I’m typing this. In a nutshell, three forms of ferroic material are widely known: ferromagnetism, ferroelectricity and ferroelasticity. But European scientists have discovered a fourth form, which they called ferrotoroidicity. This phenomenon could lead to a new way to store data on atomic roundabouts. As the lead researcher said, ‘One could compare ferrotoroidic domains with roundabouts in, say, the UK and Germany where cars go around in clockwise or counter-clockwise direction.’ Even if this discovery is very interesting, it looks like many years will pass before this ferrotoroidic effect can be used to manufacture faster and more reliable hard disks. But read more…
You can see above a diagram showing “all forms of ferroic order under the parity operations of space and time.” (Credit: Manfred Fiebig and his colleagues, via Nature) Here is a link to a larger version.
Here is a fuller explanation of what are ferrotoroidic domains. “Domains are of unparalleled technological importance as they are used for information storage and for electronic, magnetic and optical switches. They are an essential property of any ferroic material. Three forms of ferroic order are widely known: ferromagnetism, a spontaneous magnetization; ferroelectricity, a spontaneous polarization; and ferroelasticity, a spontaneous strain. It is currently debated whether to include an ordered arrangement of magnetic vortices as a fourth form of ferroic order, termed ferrotoroidicity.”
This term has been coined by Prof. Dr. Manfred Fiebig of the University of Bonn, Germany, who worked with Dutch scientist Bas Van Aken and Geneva-based physicists Hans Schmid and Jean-Pierre Rivera.
But how ferrotoroidicity can be useful to all of us? “There could also be very practical consequences in terms of technological applications. This is because magnetic vortices could be used to store information: when the atomic roundabout ‘traffic’ goes right, it could be made to stand for the binary number ‘0′; going left, it could designate the ‘1′ — a physical principle that might be introduced one day into the design of computer hard disks.”
The scientists say that current technology behind hard disk manufacturing has two limits: it’s a relatively ’slow’ process; and data can be destroyed by the magnetic fields used to create the ‘information’ on them. “The atomic roundabouts do not have these drawbacks. Here, information is also ‘magnetically’ stored but, as Manfred Fiebig points out, the ‘direction of rotation of the vortices can be changed by electrical fields.” Moreover, ‘The reading process does not require a magnet field that might overwrite the stored data by mistake.’ Another advantage is that no electricity has to flow to generate the electrical fields so, in principle, storage can run much faster.”
Reading is one thing, writing is another one. And the scientists are still working on this part, trying to write information in a reliably manner. Of course, this is just a matter of time before they solve the problem. However, believe it or not, the researchers don’t plan to make money from this discovery. “Our primary interest centres on the principles at work behind this phenomenon and what they reveal about the nature of magnetism. But if this research does result one day in a technological application, that’ll obviously be quite a bonus,” said Fiebig.
For more information, the researchers have reported their work in Nature under the name “Observation of ferrotoroidic domains” (Volume 449, Number 7163, Pages 702-705, October 11, 2007). Here is a link to the abstract. The figure above and parts of its caption were picked from this paper.
Sources: University of Bonn news release, October 10, 2007; and various websites
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