Iron-based superconductor
Encyclopedia
Iron-based superconductors (sometimes misleadingly called iron superconductors) are chemical compounds (containing iron) with superconducting properties. In 2008, led by recently discovered iron pnictide compounds (originally known as oxypnictide
s), they were in the first stages of experimentation and implementation. (Previously most high-temperature superconductors were cuprate
s and being based on layers of copper
and oxygen
sandwiched between other (typically non-metal?) substances. )
This new type of superconductors is based instead on conducting layers of iron
and a pnictide (typically arsenic
) and seems to show promise as the next generation of high temperature superconductors.
Much of the interest is because the new compounds are very different from the cuprates and may help lead to a theory of non-BCS-theory superconductivity.
More recently these have been called the ferropnictides. The first ones found belong to the group of oxypnictide
s. Some of the compounds have been known since 1995
and their semiconductive properties have been known and patented since 2006.
It has also been found that some iron chalcogen
s superconduct; for example, doped FeSe can have a critical temperature (Tc) of 8 K
at normal pressure, and 27 K under high pressure.
A subset of iron-based superconductors with properties similar to the oxypnictides, known as the 122 Iron Arsenides, attracted attention in 2008 due to their relative ease of synthesis.
The oxypnictide
s such as LaOFeAs are often referred to as the '1111' pnictides.
Compounds such as Sr2ScFePO3 discovered in 2009 are referred to as the '42622' family, as FePSr2ScO3. Noteworthy is the synthesis of (Ca4Al2O6-y)(Fe2Pn2) (or Al-42622(Pn); Pn = As and P) using high-pressure synthesis technique. Al-42622(Pn) exhibit superconductivity for both Pn = As and P with the transition temperatures of 28.3 K and 17.1 K, respectively. The a-lattice parameters of Al-42622(Pn) (a = 3.713 Å and 3.692 Å for Pn = As and P, respectively) are smallest among the iron-pnictide superconductors. Correspondingly, Al-42622(As) has the smallest As-Fe-As bond angle (102.1°) and the largest As distance from the Fe planes (1.5 Å). High-pressure technique also yields (Ca3Al2O5-y)(Fe2Pn2) (Pn = As and P), the first reported iron-based superconductors with the perovskite-based '32522' structure. The transition temperature (Tc) is 30.2 K for Pn = As and 16.6 K for Pn = P. The emergence of superconductivity is ascribed to the small tetragonal a-axis lattice constant of these materials. From these results, an empirical relationship was established between the a-axis lattice constant and Tc in iron-based superconductors.
In 2009, it was shown that undoped iron pnictides had a magnetic quantum critical point deriving from competition between electronic localization and itinerancy.
of 43 teslas
from the measured coherence length of 2.8 nm.
Oxypnictide
In chemistry, oxypnictides are a class of materials including oxygen, a pnictogen and one or more other elements...
s), they were in the first stages of experimentation and implementation. (Previously most high-temperature superconductors were cuprate
Cuprate
Cuprates are chemical compounds containing copper anion. Cuprates have been known for centuries and are widely used in inorganic and organic chemistry...
s and being based on layers of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
sandwiched between other (typically non-metal?) substances. )
This new type of superconductors is based instead on conducting layers of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
and a pnictide (typically arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
) and seems to show promise as the next generation of high temperature superconductors.
Much of the interest is because the new compounds are very different from the cuprates and may help lead to a theory of non-BCS-theory superconductivity.
More recently these have been called the ferropnictides. The first ones found belong to the group of oxypnictide
Oxypnictide
In chemistry, oxypnictides are a class of materials including oxygen, a pnictogen and one or more other elements...
s. Some of the compounds have been known since 1995
and their semiconductive properties have been known and patented since 2006.
It has also been found that some iron chalcogen
Chalcogen
The chalcogens are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family...
s superconduct; for example, doped FeSe can have a critical temperature (Tc) of 8 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
at normal pressure, and 27 K under high pressure.
A subset of iron-based superconductors with properties similar to the oxypnictides, known as the 122 Iron Arsenides, attracted attention in 2008 due to their relative ease of synthesis.
The oxypnictide
Oxypnictide
In chemistry, oxypnictides are a class of materials including oxygen, a pnictogen and one or more other elements...
s such as LaOFeAs are often referred to as the '1111' pnictides.
Compounds such as Sr2ScFePO3 discovered in 2009 are referred to as the '42622' family, as FePSr2ScO3. Noteworthy is the synthesis of (Ca4Al2O6-y)(Fe2Pn2) (or Al-42622(Pn); Pn = As and P) using high-pressure synthesis technique. Al-42622(Pn) exhibit superconductivity for both Pn = As and P with the transition temperatures of 28.3 K and 17.1 K, respectively. The a-lattice parameters of Al-42622(Pn) (a = 3.713 Å and 3.692 Å for Pn = As and P, respectively) are smallest among the iron-pnictide superconductors. Correspondingly, Al-42622(As) has the smallest As-Fe-As bond angle (102.1°) and the largest As distance from the Fe planes (1.5 Å). High-pressure technique also yields (Ca3Al2O5-y)(Fe2Pn2) (Pn = As and P), the first reported iron-based superconductors with the perovskite-based '32522' structure. The transition temperature (Tc) is 30.2 K for Pn = As and 16.6 K for Pn = P. The emergence of superconductivity is ascribed to the small tetragonal a-axis lattice constant of these materials. From these results, an empirical relationship was established between the a-axis lattice constant and Tc in iron-based superconductors.
In 2009, it was shown that undoped iron pnictides had a magnetic quantum critical point deriving from competition between electronic localization and itinerancy.
Superconductivity
Superconducting transition temperatures are listed in the tables (some at high pressure). BaFe1.8Co0.2As2 is predicted to have an upper critical fieldUpper critical field
-Upper critical field:The upper critical field is the magnetic field which completely suppresses superconductivity in a Type II superconductor at 0K ....
of 43 teslas
Tesla (unit)
The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
from the measured coherence length of 2.8 nm.
Further reading
- A selection of free-download papers on iron-based superconductors in New Journal of Physics
- "To What Extent Iron-Pnictide New Superconductors Have Been Clarified:A Progress Report" Ishida et al. June 2009
- "High Temperature Superconductivity in Iron-Based Materials" J. Paglione and R.L. Greene, Nature Physics 6, 645 (2010)
- "High-pressure synthesis and physical properties of new iron (nickel)-based superconductors" P. M. Shirage et. al. , Physica c Reveiw, (2009)
See also
- Andreev reflectionAndreev reflectionAndreev reflection , named after the Russian physicist Alexander F. Andreev, is a type of particle scattering whichoccurs at interfaces between a superconductor and a normal state material . It is a charge-transfer process by which normal current in N is converted to supercurrent in S...
- Charge transfer complexCharge transfer complexA charge-transfer complex or electron-donor-acceptor complex is an association of two or more molecules, or of different parts of one very large molecule, in which a fraction of electronic charge is transferred between the molecular entities. The resulting electrostatic attraction provides a...
- Color superconductivityColor superconductivityColor superconductivity is a phenomenon predicted to occur in quark matter if the baryon density is sufficiently high and the temperature is not too high...
in quarks - Composite Reaction TexturingComposite Reaction TexturingCRT – Composite Reaction Texturing is a process invented at the University of Cambridge by Prof. J.E.Evetts and dr B.A. Glowacki by which ceramic Bi2Sr2CaCu2O8+x superconductor with induced microstructural texture can be used for high current applications such as current leads or resistive fault...
- Conventional superconductorConventional superconductorConventional superconductors are materials that display superconductivity as described by BCS theory or its extensions.Critical temperatures of some simple metals:ElementTc Al1.20Hg4.15Mo0.92Nb9.26Pb7.19...
- covalent superconductorsCovalent superconductorsCovalent semiconductors are such solids as diamond, silicon, germanium, silicon carbide and silicon-germanium where atoms are linked by covalent bonds. Most of those materials, at least in their bulk form, are well studied and rarely hit the front pages of the top scientific journals in the last...
- High-temperature superconductivityHigh-temperature superconductivityHigh-temperature superconductors are materials that have a superconducting transition temperature above . From 1960 to 1980, 30 K was thought to be the highest theoretically possible Tc...
- Homes's law
- Kondo effectKondo effectIn physics, the Kondo effect describes the scattering of conduction electrons in a metal due to magnetic impurities. It is a measure of how electrical resistivity changes with temperature....
- Little-Parks effectLittle-Parks effectThe Little–Parks effect [1] was discovered in 1962 in experiments with empty and thin-walled superconducting cylinders subjected to a parallel magnetic field....
- Magnetic sailMagnetic sailA magnetic sail or magsail is a proposed method of spacecraft propulsion which would use a static magnetic field to deflect charged particles radiated by the Sun as a plasma wind, and thus impart momentum to accelerate the spacecraft...
- National Superconducting Cyclotron LaboratoryNational Superconducting Cyclotron LaboratoryNational Superconducting Cyclotron Laboratory is located on the campus of Michigan State University and is the leading rare isotope research facility in the United States...
- OxypnictideOxypnictideIn chemistry, oxypnictides are a class of materials including oxygen, a pnictogen and one or more other elements...
- Proximity effect
- Room temperature superconductorRoom temperature superconductorA room-temperature superconductor is a material yet to be discovered which would be capable of exhibiting superconducting properties at operating temperatures above 0° C . This is not strictly speaking "room temperature" A room-temperature superconductor is a material yet to be discovered...
- Rutherford cableRutherford cableA Rutherford cable is a type of superconducting cable used to generate magnetic fields in particle accelerators. The cables are so-called because of the Rutherford Laboratory where the cable design was developed.-External links:...
- Spallation Neutron SourceSpallation Neutron SourceThe Spallation Neutron Source is an accelerator-based neutron source facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development...
- Superconducting RF
- Superconductor classificationSuperconductor classificationSuperconductors can be classified in accordance with several criteria that depend on our interest in their physical properties, on the understanding we have about them, on how expensive is cooling them or on the material they are made of....
- Superfluid filmSuperfluid filmSuperfluidity and superconductivity are macroscopic manifestations of quantum mechanics. There is considerable interest, both theoretical and practical, in these quantum phase transitions. There has been a tremendous amount of work done in the field of phase transitions and critical phenomenon in...
- Technological applications of superconductivityTechnological applications of superconductivitySome of the technological applications of superconductivity include:* the production of sensitive magnetometers based on SQUIDs* fast digital circuits ,...
- Timeline of low-temperature technologyTimeline of low-temperature technologyThe following is a timeline of low-temperature technology and cryogenic technology .-16th century BCE – 17th century CE :...
- Type-I superconductor
- Type-II superconductorType-II superconductorA Type-II superconductor is a superconductor characterized by the formation of vortex lattices in magnetic field. It has a continuous second order phase transition from the superconducting to the normal state within an increasing magnetic field....
- Unconventional superconductorUnconventional superconductorUnconventional superconductors are materials that display superconductivity which does not conform to either the conventional BCS theory or the Nikolay Bogolyubov's theory or its extensions....