Video Experimental Relacionado
Updated: Jul 4, 2026
06:49
Radio Frequency Magnetron Sputtering of GdBa2Cu3O7−δ/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 (STO) Single-crystal Substrates
Published on: April 12, 2019
Orden magnético cercano a la superconductividad en los sistemas LaO1-xFxFeAs en capas basados en hierro
Clarina de la Cruz1, Q Huang, J W Lynn
1Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA.
Nature
|May 30, 2008
Resumen
Los investigadores encontraron evidencia directa del orden de onda de densidad de espín (SDW) en LaOFeAs, un compuesto madre clave para los superconductores a base de hierro. La supresión de este orden magnético a través del dopaje promueve la superconductividad, similar a los óxidos de cobre a alta temperatura.
Área de la Ciencia:
- Física de la materia condensada Física de la materia condensada
- Ciencia de los materiales Ciencia de los materiales.
- El magnetismo es el magnetismo.
Sus antecedentes:
- Los óxidos de cobre de alta temperatura de transición (alta T ((c)) exhiben superconductividad cercana al orden antiferromagnético.
- Los óxidos a base de hierro de tierras raras (ROFeAs) también muestran superconductividad tras el dopaje, pero la evidencia directa de orden magnético en los compuestos progenitores faltaba.
- LaOFeAs, un compuesto padre, muestra anomalías que sugieren inestabilidad magnética, pero carece de una prueba directa del orden de onda de densidad de espín (SDW).
Objetivo del estudio:
- Proporcionar evidencia experimental directa para el orden magnético de onda de densidad de espín (SDW) en el compuesto madre LaOFeAs.
- Investigar la relación entre la distorsión estructural, el orden magnético y la superconductividad en los óxidos a base de hierro.
- Comprender el papel del antiferromagnetismo en la aparición de la superconductividad en estos materiales.
Principales métodos:
- Los experimentos de dispersión de neutrones se llevaron a cabo en LaOFeAs.
- Se realizaron mediciones de resistividad y de susceptibilidad magnética a corriente continua.
- Se estudiaron los efectos del dopaje de flúor en las propiedades estructurales y magnéticas.
Principales resultados:
- LaOFeAs sufre una distorsión estructural desde la simetría tetragonal a la monoclinica por debajo de 155 K.
- El orden antiferromagnético de tipo SDW de largo alcance se desarrolla por debajo de aproximadamente 137 K.
- El dopaje de flúor suprime tanto la distorsión estructural como el orden magnético, lo que lleva a la superconductividad.
- Se encuentra que el régimen superconductor está muy cerca de un estado fundamental antiferromagnético ordenado a largo alcance.
Conclusiones:
- La evidencia directa del orden de SDW en LaOFeAs confirma su papel como precursor de la superconductividad.
- Los hallazgos establecen un paralelismo entre los superconductores a base de hierro y los óxidos de cobre de alto T (c) en cuanto a la proximidad del magnetismo y la superconductividad.
- Comprender esta interacción es crucial para el diseño de nuevos materiales superconductores.
Más Videos Relacionados
Videos de Conceptos Relacionados
01:31Ferromagnetism
Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
01:28Types Of Superconductors
A superconductor is a substance that offers zero resistance to the electric current when it drops below a critical temperature. Zero resistance is not the only interesting phenomenon as materials reach their transition temperatures. A second effect is the exclusion of magnetic fields. This is known as the Meissner effect. A light, permanent magnet placed over a superconducting sample will levitate in a stable position above the superconductor. High-speed trains that levitate on strong...
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:24Superconductor
A substance that reaches superconductivity, a state in which magnetic fields cannot penetrate, and there is no electrical resistance, is referred to as a superconductor. In 1911, Heike Kamerlingh Onnes of Leiden University, a Dutch physicist, observed a relation between the temperature and the resistance of the element mercury. The mercury sample was then cooled in liquid helium to study the linear dependence of resistance on temperature. It was observed that, as the temperature decreased, the...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
01:17Theory of Metallic Conduction
The conduction of free electrons inside a conductor is best described by quantum mechanics. However, a classical model makes predictions close to the results of quantum mechanics. It is called the theory of metallic conduction.
In this theory, Newton's second law of motion is used to determine the acceleration of an electron in the presence of an applied electric field. Then, its velocity is expressed via this acceleration.
An electron moves through the crystal, containing positive ions,...
In this theory, Newton's second law of motion is used to determine the acceleration of an electron in the presence of an applied electric field. Then, its velocity is expressed via this acceleration.
An electron moves through the crystal, containing positive ions,...