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X-ray holograms expose secret magnetism
May 03, 2007Collaborative research between scientists in the UK and USA has led to a major breakthrough in the understanding of antiferromagnets, published in this week's Nature. Scientists at the London Centre for Nanotechnology, the University of Chicago and the Center for Nanoscale Materials at Argonne National Laboratory have used x-rays to see the internal workings of antiferromagnets for the very first time.
Unlike conventional magnets, antiferromagnets (such as the metal chromium) are materials which exhibit 'secret' magnetism, undetectable at a macroscopic level. Instead, their magnetism is confined to very small regions where atoms behave as tiny magnets. They spontaneously align themselves opposite to adjacent atoms, leaving the material magnetically neutral overall.
Professor Gabriel Aeppli, Director of the London Centre for Nanotechnology, said: "People have been familiar with ferromagnets for hundreds of years and they have countless everyday uses; everything from driving electrical motors to storing information on hard disk drives. We haven't been able to make the same strides with antiferromagnets because we weren't able to look inside them and see how they were ordered.
"This breakthrough takes our understanding of the internal dynamics of antiferromagnets to where we were ninety years ago with ferromagnets. Once you can see something, it makes it that much easier to start engineering it."
The magnetic characteristics of ferromagnets have been studied by scientists since Greek antiquity, enabling them to build up a detailed picture of the regions - or "magnetic domains" - into which they are divided. However, antiferromagnets remained a mystery because their internal structure was too fine to be measured.
The internal order of antiferromagnets is on the same scale as the wavelength of x-rays (below 10 nanometers). The latest research used x-ray photon correlation spectroscopy to produce 'speckle' patterns; holograms which provide a unique 'fingerprint' of a particular magnetic domain configuration.
Dr. Eric D. Isaacs, Director of the Center for Nanoscale Materials, said: "Since the discovery of x-rays over 100 years ago, it has been the dream of scientists and engineers to use them to make holographic images of moving objects, such as magnetic domains, at the nanoscale.
"This has only become possible in the last few years with the availability of sources of coherent x-rays, such as the Advanced Photon Source, and the future looks even brighter with the development of fully coherent x-ray sources called Free Electron Lasers over the next few years."
In addition to producing the first antiferromagnet holograms, the research also showed that their magnetic domains shift over time, even at the lowest of temperatures. The most likely explanation for this can be found in quantum mechanics and the experiments open the door to the future exploitation of antiferromagnets in emerging technologies such as quantum computing.
"The key finding of our research provides information on the stability of domain walls in antiferromagnets," said Oleg Shpyrko, lead author on the publication and researcher at the Center for Nanoscale Materials. "Understanding this is the first step towards engineering antiferromagnets into useful nanoscale devices that exploit it."
University College London
"This breakthrough takes our understanding of the internal dynamics of antiferromagnets to where we were ninety years ago with ferromagnets. Once you can see something, it makes it that much easier to start engineering it."
The magnetic characteristics of ferromagnets have been studied by scientists since Greek antiquity, enabling them to build up a detailed picture of the regions - or "magnetic domains" - into which they are divided. However, antiferromagnets remained a mystery because their internal structure was too fine to be measured.
The internal order of antiferromagnets is on the same scale as the wavelength of x-rays (below 10 nanometers). The latest research used x-ray photon correlation spectroscopy to produce 'speckle' patterns; holograms which provide a unique 'fingerprint' of a particular magnetic domain configuration.
Dr. Eric D. Isaacs, Director of the Center for Nanoscale Materials, said: "Since the discovery of x-rays over 100 years ago, it has been the dream of scientists and engineers to use them to make holographic images of moving objects, such as magnetic domains, at the nanoscale.
"This has only become possible in the last few years with the availability of sources of coherent x-rays, such as the Advanced Photon Source, and the future looks even brighter with the development of fully coherent x-ray sources called Free Electron Lasers over the next few years."
In addition to producing the first antiferromagnet holograms, the research also showed that their magnetic domains shift over time, even at the lowest of temperatures. The most likely explanation for this can be found in quantum mechanics and the experiments open the door to the future exploitation of antiferromagnets in emerging technologies such as quantum computing.
"The key finding of our research provides information on the stability of domain walls in antiferromagnets," said Oleg Shpyrko, lead author on the publication and researcher at the Center for Nanoscale Materials. "Understanding this is the first step towards engineering antiferromagnets into useful nanoscale devices that exploit it."
University College London
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More Antiferromagnets Current Events and Antiferromagnets News Articles
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Nuclear magnetic resonance in ferro- and antiferromagnets, by E. A Turov (Author) | |
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Magneto-Optics and Spectroscopy of Antiferromagnets. With 125 Illustrations. by V V Eremenko (Author) | |
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Magnetic and Magnetoelastic Properties of Antiferromagnets and Superconductors (Physics Reviews) by V. V. Eremenko (Author), V. a. Sirenko (Author) | |
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Magneto-Optics and Spectroscopy of Antiferromagnets by V.V. Eremenko (Author), N.F. Kharchenko (Author), Yu.G. Litvinenko (Author), V.M. Naumenko (Author) Certain magnetic materials have optical properties that make them attractive for a wide variety of applications such as optical switches. This book describes the physics of one class of such magnetooptic materials, the insulating antiferromagnets. The authors summarize recent results concerning the structure, optical properties, spectroscopy, and magnetooptical properties of these materials. In particular, they consider magnetic phase transitions, symmetry effects, the linear magnetooptical effect, magnons, spectroscopic study of spin waves, photoinduced magnetic effects, and the effects of impurities. | |
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Magnetism in Strongly Correlated Systems: Spin Waves in Striped Phases and Checkerboard Phases, Quantum Monte Carlo Study of Spin Systems, and Antiferromagnet with Ring Exchange by Dao-Xin Yao (Author) This book presents analytic and numerical studies of magnetism in strongly correlated solid-state systems. Competing tendencies in these systems can lead to spontaneous nanoscale structures, such as stripes and checkerboards. There are three topics explored in this book. First, spin waves and magnetic excitations for well-ordered spin structures are studied by using a suitably parametrized Heisenberg model. Both site-centered and bond-centered antiphase domain walls are considered for a range of spacings between stripes and checkerboard antiphase domain walls. Second, quasi-two-dimensional spin systems are explored by using the Stochastic Series Expansion Quantum Monte Carlo method. The order-disorder phase transitions are studied for both static and dynamic bond-diluted... |
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Ising-type Antiferromagnets: Model Systems in Statistical Physics and in the Magnetism of Exchange Bias (Springer Tracts in Modern Physics) by Christian Binek (Author) The book deals with selected modern aspects of artificially layered structures and bulk materials involving antiferromagnetic long-range order. Special emphasis is laid on the prototypical behavior of Ising-type model systems. They play a crucial role in the field of statistical physics and, in addition, contribute to the basic understanding of the exchange bias phenomenon in MBE-grown magnetic heterosystems. Throughout the book, particular attention is given to the interplay between experimental results and their theoretical description, ranging from the famous Lee-Yang theory of phase transitions to novel mechanisms of exchange bias. |
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Nuclear magnetic resonance in ferro- and antiferromagnets by E. A Turov (Author) | |
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Theory of the two-sublattice Heisenberg antiferromagnet (NASA TN) by Edwin G Wintucky (Author) | |
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Microwave magnon-phonon interactions in ferromagnets and antiferromagnets, by F. R Morgenthaler (Author) | |
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Magnetostriction in ferromagnets and antiferromagnets (Massachusetts Institute of Technology. Dept. of Physics. Thesis. 1977. Ph. D) by Robert Daniel Yacovitch (Author) |
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