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用1064nm激发的近红外傅里叶变换表面增强拉曼散射技术研究腺嘌呤系列胡凤霞方炎(首都师范大学综合技术研究所,北京100037)FourierTransformSurface-EnhancedRamanSpectroscopyofSeriesofAd... 相似文献
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Large magnetic entropy change near room temperature in the LaFe11.5Si1.5H1.3 interstitial compound 总被引:2,自引:0,他引:2 下载免费PDF全文
The LaFe11.5Si1.5H1.3 interstitial compound has been prepared. Its Curie temperature TC (288 K) has been adjusted to around room temperature, and the maximal magnetic entropy change (|ΔS|~17.0 J·kg-1·K-1 at TC) is larger than that of Gd (|ΔS|~9.8 J·kg-1·K-1 at TC=293 K) by ~73.5% under a magnetic change from 0 to 5 T. The origin of the large magnetic entropy change is attributed to the first-order field-induced itinerant-electron metamagnetic transition. Moreover, the magnetic hysteresis of LaFe11.5Si1.5H1.3 under the increase and decrease of the field is very small, which is favourable to magnetic refrigeration application. The present study suggests that the LaFe11.5Si1.5H1.3 compound is a promising candidate as a room-temperature magnetic refrigerant. 相似文献
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Effect of Dy substitution on magnetic properties and magnetocaloric effects of Tb6Co1.67Si3 compounds 下载免费PDF全文
The magnetic and magnetocaloric properties of(Tb1-xDyx) 6 Co 1.67 Si 3(0 ≤ x ≤ 0.8) have been experimentally investigated.The compounds exhibit a Ce6Ni2Si3-type hexagonal structure and undergo a second-order magnetic transition.The Curie temperature decreases from ~ 187 K to 142 K as the content of Dy grows from 0 to 0.8.The maximal magnetic entropy change,for a field change of 0-5 T,varies between ~ 6.2 and ~ 7.4 J/kg.K,slightly decreasing when Dy is introduced.The substitution of Dy leads to a remarkable increase in refrigeration capacity(RC).A large RC value of ~ 626 J/kg is achieved for x = 0.4 under a field change of 0-5 T. 相似文献
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采用多种X射线衍射技术和磁电阻测量技术研究了不同厚度的La0.8Ca0.2MnO3/SrTiO3 (LCMO/STO)薄膜的应变状态及其对磁电阻性能的影响.结果表明,在STO(001)单晶衬底上生长的LCMO薄膜沿[00l]取向生长.LCMO薄膜具有伪立方钙钛矿结构,随着薄膜厚度的增加,面内晶格参数增加,垂直于面内的晶格参数减小,晶格参数a和b相近,略小于c.LC
关键词:
X射线衍射
微结构
应变
物理性能 相似文献
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La-Fe基NaZn13型化合物的磁场诱导熵变研究 总被引:3,自引:4,他引:3
围绕具有一级磁性相变的La-Fe基NaZn13型化合物的磁场诱导熵变研究,从室温磁制冷目的出发讨论了材料研究和熵变机制。La-Fe-Si在190K附近5T磁场下的熵变值可达29J.kg-1.K-1。用少量Co替代Fe,可以获得室温附近5T磁场下熵变为15J.kg-1.K-1的大熵变材料。这类材料中的熵变主要由磁有序熵变和晶格熵变组成。分析了一级磁性相变体系中磁有序熵变和晶格熵变对总熵变的贡献,并发现大的熵变来源于被晶格贡献抵消后的磁有序熵变。 相似文献
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We have studied the magnetic and magnetocaloric properties of the Er3Co compound, which undergoes ferromagnetic ordering below the Curie temperature Tc = 13 K. It is found by fitting the isothermal magnetization curves that the Landau model is appropriate to describe the Er3Co compound. The giant magnetocaloric effect (MCE) without hysteresis loss around Tc is found to result from the second-order ferromagnetic-to-paramagnetic transition. The max- imal value of magnetic entropy change is 24.5 J/kg.K with a refrigerant capacity (RC) value of 476 J/kg for a field change of 0-5 T. Large reversible MEC and RC indicate the potentiality of Er3Co as a candidate magnetic refrigerant at low temperatures. 相似文献
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We have studied the magnetic and magnetocaloric properties of the Er3 Co compound,which undergoes ferromagnetic ordering below the Curie temperature TC = 13 K.It is found by fitting the isothermal magnetization curves that the Landau model is appropriate to describe the Er3 Co compound.The giant magnetocaloric effect(MCE) without hysteresis loss around T C is found to result from the second-order ferromagnetic-to-paramagnetic transition.The maximal value of magnetic entropy change is 24.5 J/kg.K with a refrigerant capacity(RC) value of 476 J/kg for a field change of 0-5 T.Large reversible MEC and RC indicate the potentiality of Er3 Co as a candidate magnetic refrigerant at low temperatures. 相似文献
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Magnetoresistances and magnetic entropy changes associated with negative lattice expansions in NaZn13-type compounds LaFeCoSi 下载免费PDF全文
Magnetoresistances and magnetic entropy changes in NaZn13-type compounds La(Fel-xCox)11.9Si1.1 (x=0.04, 0.06, and 0.08) with Curie temperatures of 243 K, 274 K, and 301 K, respectively, are studied. The ferromagnetic ordering is accompanied by a negative lattice expansion. Large magnetic entropy changes in a wide temperature range from ~230 K to ~320 K are achieved. Raising Co content increases the Curie temperature but weakens the magnetovolume effect, thereby causing a decrease in magnetic entropy change. These materials exhibit a metallic character below Tc, whereas the electrical resistance decreases abruptly and then recovers the metal-like behaviour above Tc. Application of a magnetic field retains the transitions via increasing the ferromagnetic ordering temperature. An isothermal increase in magnetic field leads to an increase in electrical resistance at temperatures near but above Tc, which is a consequence of the field-induced metamagnetic transition from a paramagnetic state to a ferromagnetic state. 相似文献