Video Experimental Relacionado
Updated: Jul 5, 2025
07:03
Measuring Magnetically-Tuned Ferroelectric Polarization in Liquid Crystals
Published on: August 15, 2018
8.8K
Efecto magnetocalórico criogénico gigante de bajo campo en un compuesto policristalino EuB4O7
Yuanpeng Wang1,2, Junsen Xiang3, Lei Zhang2
1School of Rare earths, University of Science and Technology of China, Hefei 230026, People's Republic of China.
Journal of the American Chemical Society
|January 23, 2024
Resumen
EuB4O7 demuestra un rendimiento de refrigeración superior como una alternativa a la refrigeración con helio-3. Este compuesto logra temperaturas más bajas y tiempos de enfriamiento más largos, lo que lo hace prometedor para la refrigeración de desmagnetización adiabática.
Área de la Ciencia:
- Ciencias de los materiales
- La termodinámica
- Física de la materia condensada
Sus antecedentes:
- Los recursos de helio-3 son escasos y caros, lo que impulsa la búsqueda de tecnologías de refrigeración alternativas.
- La refrigeración por desmagnetización adiabática (ADR) es una alternativa prometedora para lograr temperaturas ultrabajas.
Objetivo del estudio:
- Investigar el magnetismo y el efecto magnetocalórico (MCE) de EuB4O7 para aplicaciones de ADR.
- Evaluar el EuB4O7 como refrigerante potencial para superar las limitaciones del helio-3.
Principales métodos:
- Medidas magnéticas para comprender el ordenamiento magnético.
- Mediciones de desmagnetización casi adiabáticas para evaluar el rendimiento del enfriamiento.
- Análisis del cambio de entropía magnética en varias intensidades de campo magnético.
Principales resultados:
- EuB4O7 no muestra un orden magnético por encima de 0,4 K, con interacciones dipolares alrededor de 800 mK.
- El cambio máximo de entropía magnética alcanzó hasta 47,6 J·kg-1·K-1 a 50 kOe.
- Alcanzó una temperatura más baja de 289 mK, superando al refrigerante comercial Gd3Ga5O12 (GGG).
- Refrigeración sostenida por debajo de 700 mK durante más de 70 minutos en un entorno de 2 K.
Conclusiones:
- EuB4O7 exhibe un efecto magnetocalórico significativo y capacidades de enfriamiento superiores.
- Este compuesto es una alternativa viable y de alto rendimiento al helio-3 para la ADR.
- La investigación adicional sobre el EuB4O7 puede avanzar en las tecnologías de refrigeración a temperaturas ultrabajas.
Videos de Conceptos Relacionados
01:31Ferromagnetism
2.4K
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...
2.4K
02:58Crystal Field Theory - Octahedral Complexes
26.5K
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
26.5K
01:30Paramagnetism
2.5K
Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
2.5K
03:02Colors and Magnetism
11.7K
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...
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...
11.7K
01:28Cryo-electron Microscopy
3.3K
Conventional electron microscopy (EM) involves dehydration, fixation, and staining of biological samples, which distorts the native state of biological molecules and results in several artifacts. Also, the high-energy electron beam damages the sample and makes it difficult to obtain high-resolution images. These issues can be addressed using cryo-EM, which uses frozen samples and gentler electron beams. The technique was developed by Jacques Dubochet, Joachim Frank, and Richard Henderson, for...
3.3K
01:28Types Of Superconductors
982
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...
982