Nanocomposites For magnetic Refrigeration

1992 ◽  
Vol 286 ◽  
Author(s):  
R.D. Shull ◽  
R.D. Mcmichael ◽  
J.J. Ritter ◽  
L.H. Bennett
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
External Magnetic Field ◽  
Magnetocaloric Effect ◽  
Spin System ◽  
Entropy Change ◽  
Magnetic Nanocomposites ◽  
Magnetic Entropy ◽  
Effect Data ◽  
The Magnetic Field

ABSTRACTUpon the application of an external magnetic field, the magnetic spins in a material partially align with the field, thereby reducing the magnetic entropy of the spin system. When performed adiabatically, the specimen's temperature will rise. This temperature rise, δT, related to the entropy change by the heat capacity, is known as the magnetocaloric effect. Upon cycling the magnetic field, this effect can be used for transferring heat from one thermal reservoir to another, forming the basis for a magnetic refrigerator. Recently, NIST scientists predicted composite magnetic materials containing nanometer-size magnetic species could possess enhanced magnetocaloric effects [1-2], especially at high temperatures or low magnetic fields. Magnetic nanocomposites may be prepared in many different ways, and recent magnetocaloric effect data measured on Fe-doped gadolinium gallium garnets are presented to show both the effect of processing and a methodology for optimizing δT.

The Influence of the Purity of Gd on the Magnetocaloric Effect in Gd5Si2-XGe2-XZn2x Alloys

2011 ◽  
Vol 685 ◽  
pp. 311-315
Author(s):  
Zhi Zeng ◽  
Xue Zhen Wang ◽  
Jian Huang ◽  
Jie Xiang ◽  
Xue Ling Hou
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetocaloric Effect ◽  
Curie Point ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
Field Change ◽  
Magnetic Field Change ◽  
Giant Magnetocaloric Effect

Gd5Si2Ge2-based alloys can exhibit a giant magnetocaloric effect (GMCE) which gives them the potential use in the cooling technologies[1].Through this studies, it can be found that the purity of Gd had a great impact on the magnetocaloric effect in Gd5Si2-xGe2-xZn2x alloys. When 3N Gd used and 2x=0.01, Gd5Si2-xGe2-xZn2x around the curie point of 280k get the maximum magnetic entropy change of 14.0 J/(Kg.K) under the external magnetic field change from 0 to 1T, but when 2N Gd used and 2x=0.05, Gd5Si2-xGe2-xZn2x around the curie point of 284.2k under the external magnetic field change 1T get the maximum magnetic entropy change 6.65 J/(Kg.K).

Magnetic Prehistory in the Heat Capacity of the Low-Temperature Superconductors

2015 ◽  
Vol 233-234 ◽  
pp. 741-744
Author(s):  
Sergey Mikhailovich Podgornykh
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
External Magnetic Field ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Zero Magnetic Field ◽  
Zero Field ◽  
Ring Specimen ◽  
Trapped Flux ◽  
The Magnetic Field

Effect of the magnetic prehistory on the temperature dependence of the heat capacity of the superconducting Pb, La, Sn. has been studied. As soon as the external magnetic field riches the valueHext=HCthe superconductivity is completely destroyed. The trapped flux was produced in the ring specimen after the magnetic field was turned off atT<TC. We observed a difference of the value of the heat capacity between zero field cooled (ZFC) and field cooled (FC) states in zero magnetic field for the ring specimen. It is found that the FC heat capacity is smaller than the heat capacity both in the normal and in superconducting states.

scholarly journals Features of Magnetocaloric Effect in Er(Co-Fe)2 Laves Phases

2016 ◽  
Vol 1 (1) ◽  
pp. 5 ◽  
Author(s):  
M.S. Anikin ◽  
E.N. Tarasov ◽  
N.V. Kudrevatykh ◽  
M.A. Semkin ◽  
A.S. Volegov ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Phase Composition ◽  
Magnetocaloric Effect ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
Concentration Increase ◽  
Laves Phases ◽  
X Ray ◽  
Temperature Range

<p>In this work the results of measurements of heat capacity (C<sub>P</sub>) and magnetocaloric effect (MCE) in Er(Co<sub>1-</sub><sub>х</sub>Fe<sub>х</sub>)<sub>2</sub> system in the concentration range 0.07 ≤ x ≤ 0.80 are presented. Phase composition was controlled by X-ray difraction analysis. Heat capacity was measured in the temperature range 77-320 K. MCE has been studied within the temperature range 5-670 K in magnetic fields up to 70 kOe. It was found that Fe concentration increase caused the table-like (plateau) MCE temperature dependence for both magnetic entropy change date and direct ∆T-effect measurements independently on Fe concentration. The possible reasons of such behavior are discussed.</p>

Magnetocaloric Effect in RFe10X2( X=Mo, V)

2018 ◽  
Vol 1 (1) ◽  
pp. 102-113
Author(s):  
Raghda Abu El-Nasr ◽  
Samy H. Aly ◽  
Sherif Yehia ◽  
Hala A. Sobh
Keyword(s):  
Heat Capacity ◽  
Magnetocaloric Effect ◽  
Magnetic Entropy Change ◽  
Mean Field ◽  
Entropy Change ◽  
Field Analysis ◽  
Electronic Contribution ◽  
Sublattice Model ◽  
Magnetic Entropy ◽  
Field Change

We present a mean-field study on the magnetocaloric effect (MCE) in RFe10X2, where X=Mo, V, and R=Gd, Tb, Ho, Tm, Dy, Er, Nd for X=V. For X=Mo, R=Dy, Gd, and Nd. The two-sublattice model, involving the 4f (rare earth) and 3d(Fe) sublattices, is used. For both systems, magnetization, magnetic heat capacity, magnetic entropy and isothermal entropy change ∆Sm are calculated for different magnetic fields in the 0-5T range and the temperature range from 0 to 700K. Direct and inverse MCEs are shown to take place in these ferromagnetic/ferrimagnetic compounds. For a field change ∆H=5T, the maximum isothermal magnetic entropy change has been calculated for ferromagnetic NdFe10Mo2 compound to be 6.6 J/K mol at Tc=441 K. Both direct, and inverse MCEs have been found in ferrimagnetic compounds, e.g., for TmFe10V2, with maximum -∆Sm= J/K mol at Tc=521K and ∆Sm=  J/K mol at TN=127 K. Mean-field analysis is suitable for handling the systems we report on. Further study on the lattice and electronic contribution to entropy is planned.

Magnetic and magnetocaloric effect in a stuffed honeycomb polycrystalline antiferromagnet GdInO3

2021 ◽  
Author(s):  
Yao-Dong Wu ◽  
Wei-Wei Duan ◽  
Qiu-Yue Li ◽  
Yong-Liang Qin ◽  
Zhen-Fa Zi ◽  
...  
Keyword(s):  
Magnetocaloric Effect ◽  
Magnetic Entropy Change ◽  
Magnetic System ◽  
Magnetic Hysteresis ◽  
Entropy Change ◽  
Cooling Power ◽  
Magnetic Entropy ◽  
Antiferromagnetic Ordering ◽  
Magnetocaloric Properties ◽  
The Magnetic Field

Abstract The magnetic and magnetocaloric properties were studied in a stuffed honeycomb polycrystalline antiferromagnet GdInO3. The onset temperature of antiferromagnetic ordering was observed at ~ 2.1 K. Negligible thermal and magnetic hysteresis suggest a reversible magnetocaloric effect (MCE) in the GdInO3 compound. In the magnetic field changes of 0–50 kOe and 0–70 kOe, the maximum magnetic entropy change values are 9.65 J/kg K and 18.37 J/kg K, respectively, near the liquid helium temperature, with the corresponding relative cooling power values of 115.01 J/kg and 211.31 J/kg. The MCE investigation of the polycrystalline GdInO3 serves to illuminate more exotic properties in this frustrated stuffed honeycomb magnetic system.

scholarly journals Tuning Magnetocaloric Properties for La-=SUB=-1-x-=/SUB=-Sr-=SUB=-x-=/SUB=-CoO-=SUB=-3-=/SUB=-

2021 ◽  
Vol 63 (10) ◽  
pp. 1551
Author(s):  
E.M. Ahmed ◽  
H.R. Alamri ◽  
S.M. Elghnam ◽  
O. Eldarawi ◽  
T.E. Tawfik ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Magnetocaloric Effect ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Paramagnetic State ◽  
Magnetic Entropy ◽  
Magnetocaloric Properties ◽  
Low Magnetic Field

Low magnetic field magnetocaloric (MC) properties of La1-xSrxCoO3 (x=0.3 and 0.5) near phase transition from a ferromagnetic to a paramagnetic state were investigated. It is shown that the change of Sr content allows MC effect in La1-xSrxCoO3 to be tunable, which is more practical for construction of MC refrigeration. MC properties of the x=0.5 sample are significantly greater than that of the x=0.3 one. Furthermore, the results show that MC properties of La1-xSrxCoO3 samples are significantly larger, and comparable with some MC properties of many materials like Gd1-xCaxBaCo2O5.5 and Ge0.95Mn0.05. Keywords: magnetocaloric effect, La1-xSrxCoO3, magnetic entropy change.

A series of new octanuclear Ln8 clusters: magnetic studies reveal a significant cryogenic magnetocaloric effect and slow magnetic relaxation

2019 ◽  
Vol 43 (3) ◽  
pp. 1617-1625 ◽  
Author(s):  
Ling-Fei Li ◽  
Wei-Wei Kuang ◽  
Yi-Ming Li ◽  
Li-Li Zhu ◽  
Yun Xu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Direct Current ◽  
Magnetic Relaxation ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
Magnetic Studies ◽  
Slow Magnetic Relaxation ◽  
Current Magnetic Field

A series of new octanuclear Ln8 clusters. Magnetically, Gd8 exhibited a significant magnetocaloric effect and a magnetic entropy change is 32.49 J K−1 kg−1 for a field of 7 T at 2 K, while Dy8 exhibited a frequency dependent slow relaxation of magnetization at a zero applied direct current magnetic field.

Room Temperature Magnetocaloric Effect of the Cox(MnSb)1-x Compounds

2013 ◽  
Vol 683 ◽  
pp. 56-59 ◽  
Author(s):  
Jian Hua Lin ◽  
Shan Dong Li ◽  
Li Li Wang ◽  
Jie Qiu ◽  
Zhi Yi Cai ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Room Temperature ◽  
Magnetic Entropy Change ◽  
Magnetic Hysteresis ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
Thermal Lag ◽  
Magnetocaloric Materials ◽  
Curie Temperature Tc

The room-temperature magnetocaloric effect (MCE) of Cox(MnSb)1-x (x=0.07, 0.15, 0.24) alloys has been investigated. It is revealed that the Curie temperature TC and the magnetic entropy change ΔSM are sensitive to the Co content x. When x=0.15, the MCE of Co0.15(MnSb)0.85 alloy is optimal with ΔSM=1.8 J/kg.K at 324 K under an applied magnetic field of 3 T. A second-order phase transformation occurs around TC, and the magnetic hysteresis loss thermal lag is negligible. These features demonstrate that Co0.15(MnSb)0.85 alloy is a promising room-temperature magnetocaloric materials.

The Effect of Magnetic Field on the Hydration of Nanoscopic Hydrophobic N-Alkane Plates

2011 ◽  
Vol 228-229 ◽  
pp. 1007-1011
Author(s):  
Wei Wei Zhang ◽  
Long Qiu Li ◽  
Guang Yu Zhang ◽  
Hui Juan Dong
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Dynamics Simulation ◽  
Free Energy Barrier ◽  
Confined Water ◽  
Magnetic Exposure ◽  
Hydrophobic Solutes ◽  
The Magnetic Field ◽  
Density Of Water ◽  
Induced Adsorption

The effect of an external magnetic field on the hydration behavior of nanoscopic n-octane plates has been extensively investigated using molecular dynamics simulation in an isothermal-isobaric ensemble. The solute plates with different intermolecular spacing have also been considered to examine the effect of the topology of hydrophobic plates on the adsorption behavior of confined water in the presence of an external magnetic field with an intensity ranging from 0.1T to 1 T. The results demonstrate that magnetic exposure decreases the density of water for the plates with intermolecular spacing of a0 = 4 and 5 Å. This suggests that the free energy barrier for evaporation can be lowered by the applied field, and the hydrophobic solutes consisting of condensed n-octane molecules are apt to aggregate in the aqueous solution. In contrast, the magnetic field improves the dissolution or wetting of solutes comprised of loosely packed n-octane plates of a0=7Å. A magnetic-field-induced adsorption-to-desorption translation, which is in agreement with the experimental results provided by Ozeki, has also been observed for the plates with intermolecular spacing of a0 = 6 Å.

Large magnetic entropy change at cryogenic temperature in rare earth HoN nanoparticles

RSC Advances ◽  
2016 ◽  
Vol 6 (79) ◽  
pp. 75562-75569 ◽  
Author(s):  
K. P. Shinde ◽  
S. H. Jang ◽  
M. Ranot ◽  
B. B. Sinha ◽  
J. W. Kim ◽  
...  
Keyword(s):  
Rare Earth ◽  
Low Temperature ◽  
Magnetocaloric Effect ◽  
Cryogenic Temperature ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Environmental Problems ◽  
Magnetic Refrigeration ◽  
Magnetic Entropy ◽  
Alternative Technology

The most extensive cooling techniques based on gases have faced environmental problems. The magnetic refrigeration is an alternative technology based on magnetocaloric effect. HoN nanoparticles are good refrigerant material at low temperature.

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