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Magnetic Storage Using Quantum Vortex Cores
brian0918 writes, "Researchers at the Max Planck Institute have discovered a new, easy way to manipulate the state of tiny magnetic structures, called vortex cores, quickly and without loss. From their press release: 'Up until now, very strong magnetic fields have been necessary to accomplish this, requiring highly complex technology. The new method might open up new possibilities for magnetic data storage. The directions of the small nanoscopic magnetic needles define a digital bit that is extremely stable in the face of frequently unavoidable external factors such as heat or interference from magnetic fields.'" You can read the first paragraph of the paper at Nature; subscribers can read it all.
Core memory eh? Why we used that in computers back when I was a kid!
gyrations of the vortex structure can be reversed by applying short bursts of the sinusoidal excitation field with amplitude of about 1.5 mT
We can turn the really small cones upside down by shooting it with 1.5 mili Tesla magnetic fields. Before we needed 500 times as much energy. I think that covers it.
Does a line appended to your comment give your post meaning in and of itself, or only in relation to those without?
The continuous downscaling in microfabrication technology has enabled the creation of magnetic microstructures and nanostructures with defined sizes and shapes. These structures are currently not only implemented in applications such as data storage and non-volatile magnetic random access memory (MRAM), but also form an interesting playground for the fundamental studies of magnetism on a microscopic level.
In thin film structures, in which the magnetostatic interactions usually force the magnetization to lie parallel to the film plane, typical magnetic configurations occur with domain structures that close the magnetic flux. Square patterns have in this case a typical Landau structure with four triangular domains separated by 90 domain walls. The magnetic vortex is located at the centre of this domain structure, where the four domains meet one another. The curling magnetization cannot stay in the plane at the very centre of the vortex structure because the short-range exchange interaction favours a parallel alignment of neighbouring magnetic moments. The magnetization turns perpendicular to the plane in an area with a radius of about 10 nm, in this way forming the vortex core7. The direction of the out-of-plane component of the magnetization is defined as the polarization of the vortex core (up or down) and gives, together with the sense of the in-plane flux closure (clockwise or anticlockwise), the ground-state configuration as illustrated in Fig. 1a-c. A magnetic vortex can store two bits of information13: the sense of the in-plane flux closure can be used as an information carrier (Fig. 1a, b)14, 15, and the out-of-plane polarization of the magnetic vortex core can also be regarded as '0' or '1' of a bit element (Fig. 1a, c). However, to switch the vortex core polarization, magnetic fields of the order of 0.5 T (refs 16, 17) are needed.
Figure 1: Three-dimensional and two-dimensional representation of vortex and antivortex structures.
Figure 1 : Three-dimensional and two-dimensional representation of vortex and antivortex structures. Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, or to obtain a text description, please contact npg@nature.com
Vortex (a, b and c) and antivortex (d) structures are illustrated. In both cases the magnetization turns out of the plane at the centre of the structure--either up (a, b, d) or down (c)--corresponding to the vortex core polarization p. In addition, vortex structures are characterized by an in-plane flux closure, which can be clockwise (b) or anticlockwise (a, c). A three-dimensional representation is on the left of each panel; a two-dimensional scheme is on the right. The arrows in the two-dimensional schemes represent the in-plane magnetization components; while the coloured dots represent the out-of-plane component (blue, up; red, down).
High resolution image and legend (298K)
Here we report on experimental studies towards an easy and reproducible switching of the vortex core polarization by low-field excitations. The dynamics in micrometre-sized and square ferromagnetic Permalloy elements with a Landau magnetic ground state were investigated. The structures were excited with an in-plane sinusoidal magnetic field resulting in a gyrotropic movement of the vortex core around the equilibrium position. As already verified in magneto-optical measurements, this in-plane gyrotropic mode is the lowest excitation mode in elements exhibiting a vortex structure (in the frequency range 100 MHz to 1 GHz (refs 18, 19)). A general theory on the dynamics of magnetic domain structures has been introduced previously8. The sense of gyration of a vortex structure is given by the gyrocoupling vector G = -2piqpUnfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, or to obtain a text description, please contact npg@nature.com, where q is the topological vorticity, p the vortex core polarization, and Unfortunately
average user can't afford it yes but it does not mean it is not useable. turner networks has been using holographic storage for their media for quite some time now. http://www.inphase-technologies.com/news/turnerona ir.html
The paper cites 10nm radius for the cores, which at optimal packing (ie, one core per 20nm square) yields 3.12500 * 10^14 Bytes / m^2. The latest in perpendicular recording gives an areal density of 277.1 Mb/mm^2, which is just 3.46375 * 10^13 Bytes / m^2, an order of magnitude less! Granted, packing is probably not optimal -- the cores probably need to be spaced by at least a multiple of their diameter. But then again, the cores can probably be shrunk, so at the very least this represents a modest improvement over current storage density. At best, it represents at least an order of magnitude improvement (read: 7.5 TB desktop drives).
:)
PS: Slashdot -- please add support for mathml or latex code inserts
Mangetic storage is supposed to replace DRAM, because its non-volitile and faster, because of this it may also end up replacing all storage in computers, if they can get density high enough. They want this for "instant on" machines that dont need time to turn on because everything is already in RAM) It doesnt require an electron microscope to read it though, and its all done at room temperature (to the best of my knowledge).
It's called MRAM for a reason...