The crystal structure, itinerant-electron metamagnetic transition (IEMT) and magnetocaloric effect (MCE) in the iron-based rare-earth intermetallic compound La0.8Ce0.2Fe11.4Si1.6 have been investi- gated. The powder X...The crystal structure, itinerant-electron metamagnetic transition (IEMT) and magnetocaloric effect (MCE) in the iron-based rare-earth intermetallic compound La0.8Ce0.2Fe11.4Si1.6 have been investi- gated. The powder X-ray diffraction revealed that the ingot of La0.8Ce0.2Fe11.4Si1.6 annealed at 1373 K in vacuum for only 5 days could be crystallized in the cubic NaZn13-type structure. The La0.8Ce0.2Fe11.4Si1.6 compound exhibited giant values of the isothermal entropy change ?SM around the Curie temperature TC (about 186 K). And the maximum value ΔS M max is about 78.29 J/(kg·K) under a field change of 0—3 T, which can be calculated by the magnetization iso- therms around TC. Such a large MCE is attributed to the sharp change of magnetization and susceptibility around TC and the first-order magnetic transition of field-induced IEMT above TC.展开更多
The FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites were prepared by hot pressing(HP). The microstructure,corrosion behavior and magnetocaloric effect(MCE) of FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites were investiga...The FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites were prepared by hot pressing(HP). The microstructure,corrosion behavior and magnetocaloric effect(MCE) of FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites were investigated systematically. The results show that the corrosion resistance of FeNi coated LaFe_(11.6)Si_(1.4)Sn composites is better than that of LaFe_(11.6)Si_(1.4)/Sn composites in deionized water. The maximum magnetic entropy change((-△S_M)^(max)) and relative cooling power(RCP) of FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites are 13.30 J/(kg-K) and 146.25 J/kg, respectively, which are larger than that((-△S_M)^(max), 10.65 J/(kg·K) and RCP, 106.53 J/kg) of LaFe_(11.6)Si_(1.4)/Sn composites in a low magnetic field change of 2 T. FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites possess a more negative slope. The improvement of magnetic properties is due to high permeability FeNi permalloy(1 J85) which improves the itinerant-electron metamagnetic(IEM) transition. So, the method of coating FeNi can provide a new idea for enhancing the corrosion resistance and magnetocaloric effect of La(Fe_xSi_(1-x))_(13)-based materials.展开更多
Crystal structure, magnetic properties and magnetocaloric effects （MCE） of La1-xBixFe1 1.4Si1.6 （x=0.0 and 0.1） compounds were investigated by X-ray diffraction and magnetization measurements. The La1-xBixFe11.4Si...Crystal structure, magnetic properties and magnetocaloric effects （MCE） of La1-xBixFe1 1.4Si1.6 （x=0.0 and 0.1） compounds were investigated by X-ray diffraction and magnetization measurements. The La1-xBixFe11.4Si1.6 compounds presented a cubic NaZnx3 type structure. First, the magnetization behavior and the magnetic transition were analyzed in terms of Landau theory. Then, Bi substitution for La in La1-xBixFe11.4Si1.6 compounds led to a decrease in magnetic entropy change （-△SM^max） but an increase in Curie temperature （Tc） significantly. The significant increase of Tc by Bi substitution from 202.5 to 256 K for x=0.0 and x=0.1 respectively was attributed to an increase in the Fe-Fe exchange interactions. Moreover, magnetocaloric effect was calculated in terms of isothermal magnetic entropy change. The maximum values of （-△SM^max ） of La1-xBixFe11.4Si1.6 for x=-0.0 and 0.1 compounds were found to be, respectively, 22.56 and 4.36 J/（kg.K） under an applied magnetic field change of 5 T. For the same applied magnetic field （μ0H=5 T）, the relative cooling power （RCP） values were found to vary between 487 and 296 J/kg.展开更多
The magnetocaloric effect of LaFe11.7Si1.3 compound was investigated under an external magnetic field up to 9 T.The magnetization changed drastically at the Curie temperature TC under different fields and TC increased...The magnetocaloric effect of LaFe11.7Si1.3 compound was investigated under an external magnetic field up to 9 T.The magnetization changed drastically at the Curie temperature TC under different fields and TC increased with the applied fields.The magnetic entropy change ｜？SM｜ vs temperature peak consisted of a spike and a plateau.The spike was a spurious result,while the plateau part resulted from the field-induced itinerant-electron metamagnetic（IEM） transition above TC,which went up with magnetic fields increasing.The width of the magnetic entropy change increased with magnetic fields at a rate of dL？S /dT^4 K/T.展开更多
Magnetic properties and magnetic entropy changes in LaFe11.5Si1.5 have been investigated by partially substituting Pr by La. It is found that La1-xPrxFe11.5Si1.5 compounds remain cubic NaZn13-type structures even when...Magnetic properties and magnetic entropy changes in LaFe11.5Si1.5 have been investigated by partially substituting Pr by La. It is found that La1-xPrxFe11.5Si1.5 compounds remain cubic NaZn13-type structures even when the Pr content is increased to 0.5, i.e. x = 0.5. Substitution of Pr for La leads to a reduction in both the crystal constant and the Curie temperature. A stepwise magnetic behaviour in the isothermal magnetization curves is observed, indicating that the characteristic of the itinerant electron metamagnetic （IEM） transition above Tc becomes more prominent with the Pr content increasing. As a result, the magnetic entropy change is remarkably enhanced from 23.0 to 29.4 J/kg·K as the field changes from 0 to 5T, with the value of x increasing from 0 to 0.5. It is more attractive that the magnetic entropy changes for all samples are shaped into high plateaus in a wide range of temperature, which is highly favourable for Ericsson-type magnetic refrigeration.展开更多
通过电弧炉熔炼法制备了LaFe11.4Si1.6-x P x（x=0.05,0.1,0.2,0.3）系列合金,XRD分析表明少量P元素替代,LaFe11.4Si1.6-x P x（x=0.05,0.1,0.2和0.3）合金仍然保持NaZn13型结构,但晶格常数减小。在居里温度T c附近磁化曲线表明,该系列...通过电弧炉熔炼法制备了LaFe11.4Si1.6-x P x（x=0.05,0.1,0.2,0.3）系列合金,XRD分析表明少量P元素替代,LaFe11.4Si1.6-x P x（x=0.05,0.1,0.2和0.3）合金仍然保持NaZn13型结构,但晶格常数减小。在居里温度T c附近磁化曲线表明,该系列合金经历由磁场引起巡游电子由顺磁态到铁磁态变磁转变的一级相变。随着P含量的增加,LaFe11.4Si1.6-x P x（x=0.05,0.1和0.2）的居里温度T c减小,等温磁熵变也减小。在外加磁场变化为0~1.5 T时,等温磁熵变最大值分别为19.3 J/（kg·K）,15.3 J/（kg·K）和10.3 J/（kg·K）。展开更多
基金This work was supported by the National Natural Science Foundation of China （Grant No. 50164003）.
文摘The crystal structure, itinerant-electron metamagnetic transition (IEMT) and magnetocaloric effect (MCE) in the iron-based rare-earth intermetallic compound La0.8Ce0.2Fe11.4Si1.6 have been investi- gated. The powder X-ray diffraction revealed that the ingot of La0.8Ce0.2Fe11.4Si1.6 annealed at 1373 K in vacuum for only 5 days could be crystallized in the cubic NaZn13-type structure. The La0.8Ce0.2Fe11.4Si1.6 compound exhibited giant values of the isothermal entropy change ?SM around the Curie temperature TC (about 186 K). And the maximum value ΔS M max is about 78.29 J/(kg·K) under a field change of 0—3 T, which can be calculated by the magnetization iso- therms around TC. Such a large MCE is attributed to the sharp change of magnetization and susceptibility around TC and the first-order magnetic transition of field-induced IEMT above TC.
基金Project supported by the Key Project of National Natural Science Foundation of China(51176065)
文摘The FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites were prepared by hot pressing(HP). The microstructure,corrosion behavior and magnetocaloric effect(MCE) of FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites were investigated systematically. The results show that the corrosion resistance of FeNi coated LaFe_(11.6)Si_(1.4)Sn composites is better than that of LaFe_(11.6)Si_(1.4)/Sn composites in deionized water. The maximum magnetic entropy change((-△S_M)^(max)) and relative cooling power(RCP) of FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites are 13.30 J/(kg-K) and 146.25 J/kg, respectively, which are larger than that((-△S_M)^(max), 10.65 J/(kg·K) and RCP, 106.53 J/kg) of LaFe_(11.6)Si_(1.4)/Sn composites in a low magnetic field change of 2 T. FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites possess a more negative slope. The improvement of magnetic properties is due to high permeability FeNi permalloy(1 J85) which improves the itinerant-electron metamagnetic(IEM) transition. So, the method of coating FeNi can provide a new idea for enhancing the corrosion resistance and magnetocaloric effect of La(Fe_xSi_(1-x))_(13)-based materials.
文摘Crystal structure, magnetic properties and magnetocaloric effects （MCE） of La1-xBixFe1 1.4Si1.6 （x=0.0 and 0.1） compounds were investigated by X-ray diffraction and magnetization measurements. The La1-xBixFe11.4Si1.6 compounds presented a cubic NaZnx3 type structure. First, the magnetization behavior and the magnetic transition were analyzed in terms of Landau theory. Then, Bi substitution for La in La1-xBixFe11.4Si1.6 compounds led to a decrease in magnetic entropy change （-△SM^max） but an increase in Curie temperature （Tc） significantly. The significant increase of Tc by Bi substitution from 202.5 to 256 K for x=0.0 and x=0.1 respectively was attributed to an increase in the Fe-Fe exchange interactions. Moreover, magnetocaloric effect was calculated in terms of isothermal magnetic entropy change. The maximum values of （-△SM^max ） of La1-xBixFe11.4Si1.6 for x=-0.0 and 0.1 compounds were found to be, respectively, 22.56 and 4.36 J/（kg.K） under an applied magnetic field change of 5 T. For the same applied magnetic field （μ0H=5 T）, the relative cooling power （RCP） values were found to vary between 487 and 296 J/kg.
基金supported by the National Natural Science Foundation of China(10304004)
文摘The magnetocaloric effect of LaFe11.7Si1.3 compound was investigated under an external magnetic field up to 9 T.The magnetization changed drastically at the Curie temperature TC under different fields and TC increased with the applied fields.The magnetic entropy change ｜？SM｜ vs temperature peak consisted of a spike and a plateau.The spike was a spurious result,while the plateau part resulted from the field-induced itinerant-electron metamagnetic（IEM） transition above TC,which went up with magnetic fields increasing.The width of the magnetic entropy change increased with magnetic fields at a rate of dL？S /dT^4 K/T.
基金Project supported by the National Natural Science Foundation of China （Grant No 50571112）, the National Basic Reseaxch Program of China （Grant No 2006CB601101） and the Program of Chinese Academy of Sciences （Grant No KJCX2-YW-W02）.
文摘Magnetic properties and magnetic entropy changes in LaFe11.5Si1.5 have been investigated by partially substituting Pr by La. It is found that La1-xPrxFe11.5Si1.5 compounds remain cubic NaZn13-type structures even when the Pr content is increased to 0.5, i.e. x = 0.5. Substitution of Pr for La leads to a reduction in both the crystal constant and the Curie temperature. A stepwise magnetic behaviour in the isothermal magnetization curves is observed, indicating that the characteristic of the itinerant electron metamagnetic （IEM） transition above Tc becomes more prominent with the Pr content increasing. As a result, the magnetic entropy change is remarkably enhanced from 23.0 to 29.4 J/kg·K as the field changes from 0 to 5T, with the value of x increasing from 0 to 0.5. It is more attractive that the magnetic entropy changes for all samples are shaped into high plateaus in a wide range of temperature, which is highly favourable for Ericsson-type magnetic refrigeration.
文摘通过电弧炉熔炼法制备了LaFe11.4Si1.6-x P x（x=0.05,0.1,0.2,0.3）系列合金,XRD分析表明少量P元素替代,LaFe11.4Si1.6-x P x（x=0.05,0.1,0.2和0.3）合金仍然保持NaZn13型结构,但晶格常数减小。在居里温度T c附近磁化曲线表明,该系列合金经历由磁场引起巡游电子由顺磁态到铁磁态变磁转变的一级相变。随着P含量的增加,LaFe11.4Si1.6-x P x（x=0.05,0.1和0.2）的居里温度T c减小,等温磁熵变也减小。在外加磁场变化为0~1.5 T时,等温磁熵变最大值分别为19.3 J/（kg·K）,15.3 J/（kg·K）和10.3 J/（kg·K）。
