Physicists offer new theory for iron compounds

March 13, 2009

An international team of physicists from the United States and China this week offered a new theory to both explain and predict the complex quantum behavior of a new class of high-temperature superconductors.

The findings, which are available online this week from the Proceedings of the National Academy of Sciences, are about materials known as iron pnictides (pronounced NIK-tides). The discovery of high-temperature superconductivity in pnictides a year ago is a boon for physicists who have struggled for more than two decades to explain the phenomena based on observations from a class of copper-based superconductors called cuprates (pronounced COO-prayts).

"Our research addresses the quantum magnetic fluctuations that have been observed in iron pnictides and offers a theory to explain how electron-electron interactions govern this behavior," said study co-author Qimiao Si, a physicist from Rice University. "The origins of superconductivity are believed to be rooted in these effects, so understanding them is extremely important."

In the PNAS paper, Si and collaborators from Rutgers University, Zhejiang University and the Los Alamos National Laboratory explain some of the similarities and differences between cuprates and pnictides. Under certain circumstances, the atomic arrangements in both materials cause electrons to behave collectively, marching in lock step with one another. Experimental physicists study how changes in temperature, magnetic fields and the like cause the coordinated effects to change. They also look for changes arising from differences in the way the compounds are prepared, such as when other substances are added via a technique called "doping."

"In cuprates, the parent compounds are not metallic, and they only become superconducting when they are doped," said Rutgers University physicist and co-author Elihu Abrahams. "In contrast, the parent compounds of pnictides are metallic, but like the undoped cuprates they exhibit a quantum magnetic property called antiferromagnetism."

Based on what's known about electron-electron interactions and about antiferromagnetism in other metals, the authors created a theoretical framework to explain the behavior of the pnictides, offering some specific predictions about how they will behave as they change phases.

Matter is commonly transformed when it changes phases; the melting of ice, for example, marks water's change from a solid phase to a liquid phase. In materials like cuprates and pnictides, the tendency of electrons to act in concert can lead to "quantum" phase changes, shifts from one phase to another that arise entirely from the movements of subatomic particles. The study of quantum "critical points," the tipping points that mark these phase changes, is known as "quantum criticality."

"Our work opens up the iron pnictides as a new setting to study the rich complexities of quantum criticality," said Si. "This is much needed since quantum critical points, which are believed to be important for a wide range of quantum materials, have so far been observed in only a small number of materials."

Rice University

---

---

	The 2009-2014 World Outlook for Iron Compounds Excluding Iron Oxides, Hydroxides, and Ferric Chloride by Icon Group (Author) This econometric study covers the world outlook for iron compounds excluding iron oxides, hydroxides, and ferric chloride across more than 200 countries. For each year reported, estimates are given for the latent demand, or potential industry earnings (P.I.E.), for the country in question (in millions of U.S. dollars), the percent share the country is of the region and of the globe. These comparative benchmarks allow the reader to quickly gauge a country vis-à-vis others. Using econometric models which project fundamental economic dynamics within each country and across countries, latent demand estimates are created. This report does not discuss the specific players in the market serving the latent demand, nor specific details at the product level. The study also does not consider...
	The 2009 Report on Iron Compounds Excluding Iron Oxides, Hydroxides, and Ferric Chloride: World Market Segmentation by City by Icon Group International (Author) This report was created for global strategic planners who cannot be content with traditional methods of segmenting world markets. With the advent of a "borderless world", cities become a more important criteria in prioritizing markets, as opposed to regions, continents, or countries. This report covers the top 2000 cities in over 200 countries. It does so by reporting the estimated market size (in terms of latent demand) for each major city of the world. It then ranks these cities and reports them in terms of their size as a percent of the country where they are located, their geographic region (e.g. Africa, Asia, Europe, Middle East, North America, Latin America), and the total world market. In performing various economic analyses for its clients, I have been occasionally asked...
	The 2011-2016 World Outlook for Iron Compounds Excluding Iron Oxides, Hydroxides, and Ferric Chloride by Icon Group International (Author) This econometric study covers the world outlook for iron compounds excluding iron oxides, hydroxides, and ferric chloride across more than 200 countries. For each year reported, estimates are given for the latent demand, or potential industry earnings (P.I.E.), for the country in question (in millions of U.S. dollars), the percent share the country is of the region and of the globe. These comparative benchmarks allow the reader to quickly gauge a country vis-a-vis others. Using econometric models which project fundamental economic dynamics within each country and across countries, latent demand estimates are created. This report does not discuss the specific players in the market serving the latent demand, nor specific details at the product level. The study also does not consider...
	The 2011 Report on Iron Compounds Excluding Iron Oxides, Hydroxides, and Ferric Chloride: World Market Segmentation by City by Icon Group International (Author) This report was created for global strategic planners who cannot be content with traditional methods of segmenting world markets. With the advent of a "borderless world", cities become a more important criteria in prioritizing markets, as opposed to regions, continents, or countries. This report covers the top 2000 cities in over 200 countries. It does so by reporting the estimated market size (in terms of latent demand) for each major city of the world. It then ranks these cities and reports them in terms of their size as a percent of the country where they are located, their geographic region (e.g. Africa, Asia, Europe, Middle East, North America, Latin America), and the total world market. In performing various economic analyses for its clients, I have been occasionally asked...
	Iron Compounds in Organic Synthesis (Best Synthetic Methods) by A. M. Pearson (Author), Alan R. Katritzky (Series Editor), O. Meth-Cohn (Series Editor), C. S. Rees (Series Editor) Since the 1950s, the number and nature of known organometallic compounds has increased at a bewildering pace. Organoiron compounds have played a central role in the development of the subject. Iron forms stable complexes with a wide range of ligands, making this possibly the most versatile metal in the Periodic Table. Despite this fact, the use of organoiron complexes in organic synthesis has been somewhat restricted compared with palladium, rhodium, and other metalsthat are traditionally used in catalytic processes. This book provides skillful and accessible coverage of the applications of organoiron complexes in organic synthesis specifically for the practicing organic chemist, and, similarly, the majority of the complexes discussed are easy to prepare. The book will enable...
	Iron Oxides in the Laboratory: Preparation and Characterization by Udo Schwertmann (Author), Rochelle M. Cornell (Author) Iron Oxides play an important role in numerous disciplines. Since the publication of the first edition, there has been a surge of interest in synthetic fine to ultrafine iron oxides in a wide range of scientific and technological disciplines, especially in mineralogy, geosciences and environmental science and in various branches of technology. As before, the main aim of the second edition is to present reliable, well-tested, up-to-date methods of synthesizing pure iron oxides. The section on monodispersed particles, presently of great interest to industry, has been expanded. Furthermore the methods of characterization have been focused on their relevance to iron oxides. The well tried syntheses have been retained and some new ones have been incorporated.
	Crystallographic and Structural Analysis of Iron Carbonyls by Milan Melnik (Author), Iveta Ondrejkovicova (Author), Vlasta Vancova (Author), Maria Kabesova (Author), Clive E. Holloway (Author) Contents: Abbreviations; Chapter 1: Introduction; Chapter 2: Mononuclear Iron Carbonyls; Chapter 3: Binuclear Iron Carbonyls; Chapter 4: Trinuclear Iron Carbonyls; Chapter 5: Tetranuclear Iron Carbonyls; Chapter 6: Pentanuclear Iron Carbonyls; Chapter 7: Hexanuclear Iron Carbonyls; Chapter 8: Hepta -- and Octanuclear Iron Carbonyls; Chapter 9: Conclusions; Chapter 10: Acknowledgements; Chapter 11: References; Index.
	Reducing surface defects with proper vein reduction: while vein reduction compounds can lead to improvements in iron castings--such as reduction in ... reduction.: An article from: Modern Casting by Victor S. LeFay (Author), Stephen L. Neltner (Author) This digital document is an article from Modern Casting, published by American Foundrymen's Society, Inc. on August 1, 2003. The length of the article is 1555 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser. Citation Details Title: Reducing surface defects with proper vein reduction: while vein reduction compounds can lead to improvements in iron castings--such as reduction in metal penetration and core erosion--they can result in varying degrees of tensile property reduction. Author: Victor S. LeFay Publication: Modern Casting (Magazine/Journal) Date: August 1, 2003 Publisher: American...
	The 2006-2011 World Outlook for Iron Compounds Excluding Iron Oxides, Hydroxides, and Ferric Chloride b WHAT IS LATENT DEMAND AND THE P.I.E.? The concept of latent demand is rather subtle. The term latent typically refers to something that is dormant, not observable, or not yet realized. Demand is the notion of an economic quantity that a target population or market requires under different assumptions of price, quality, and distribution, among other factors. Latent demand, therefore, is commonly defined by economists as the industry earnings of a market when that market becomes accessible and attractive to serve by competing firms. It is a measure, therefore, of potential industry earnings (P.I.E.) or total revenues (not profit) if a market is served in an efficient manner. It is typically expressed as the total revenues potentially extracted by firms. The “market” is defined at...
	Elimination of phenol and aromatic compounds by zero valent iron and EDTA at low temperature and atmospheric pressure [An article from: Chemosphere] by I. Sanchez (Author), F. Stuber (Author), J. Font (Author), A. Fortuny (Author), Fabreg (Author) This digital document is a journal article from Chemosphere, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser. Description: This work deals with a new abiotic oxidation process designed as a suitable pre-treatment step within a biological depuration of wastewater containing phenol or its derivatives (o-cresol, 2-chlorophenol and p-nitrophenol) or aniline. The reaction was carried out in a stirred tank reactor at 20^oC and atmospheric pressure in presence of the organic compound, 150mgl^-^1, zero valent iron particles (10g), ethylenediamine tetraacetic acid (EDTA, 101mgl^-^1) and air. The experimental results show that 85% of phenol conversion...