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magnetocaloric effect of LaFe_(11.35)Co_(0.6)Si_(1.05) alloy

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Rare Metals 2022年第5期41卷 1563-1569页

作者： Piotr Gebara Institute of Physics Czestochowa University of Technology42-200 CzestochowaPoland

The aim of the present paper was to study the large magnetocaloric effect observed in LaFe_(11.35)Co_(0.6)Si_(1.05)alloy. X-ray diffraction(XRD) result reveals a coexistence of two crystalline phases: a dominant La(Fe,Si)_(13)-type and a minor a-Fe(Co,Si). It is confirmed by the Mössbauer spectroscopy and microstructural observations accompanied by an energy-dispersive spectroscopy(EDS) analysis. The value of the magnetic entropy changes(|S_(M)|) in the vicinity of the Curie temperature(TC= 268 K) was calculated using thermomagnetic Maxwell relation, and it equals to 21.4 J·kg^(-1)·K^(-1) under the change in an external magnetic field of μ_(0)ΔH = 3T. The investigation of magnetic phase transition was carried out using the Landau theory, an analysis of the field dependences of the magnetic entropy change and universal scaling curve, revealing the second order of phase transition in the studied material.

关键词： X-ray diffraction M?ssbauer spectroscopy magnetocaloric effect

magnetocaloric effect and slow magnetic relaxation behavior in binuclear rare earth based RE_(2)(L)_(2)(DMF)4(RE=Gd,Tb,and Dy) complexes

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Journal of Rare Earths 2022年第6期40卷 916-923,I0003页

作者： Zhenqian Zhang Yuwei Wu Haifeng Wang Lingwei Li Key Laboratory of Novel Materials for Sensor of Zhejiang Province Institute of Advanced Magnetic MaterialsHangzhou Dianzi UniversityHangzhou 310012China State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi'an 710072China Key Laboratory of Electromagnetic Processing of Materials(Ministry of Education) Northeastern UniversityShenyang 110819China

Three binuclear rare earth based complexes combining RE ions with semirigid tricarboxylic ligand(H_(3)L).namely,[RE_(2)(L)_(2)(DMF)_(4)][RE=Gd,Tb,and Dy;H_(3)L=5-((4-Carboxybenzyl)oxy)isophthalic acid;DMF=N,N-dimethylformamide]complexes,were fabricated success *** RE_(2)(L)_(2)(DMF)_(4) co mplexe s consist of two central RE ions with the same coordination environment which were connected by two tridentate bridging carboxylic groups and two syn-syn bidentate bridging carboxylic groups originating from the L^(3-)ligands to form the{RE_(2)}dimeric unit,and thus provides the basis for further constructing a dense three-dimensional(3 D)network ***,the present RE_(2)(L)_(2)(DMF)_(4) complexes can be described by a topology diagram with the topology point symbol of{4^(2)·6}_(2){4^(4)·6^(2)·8^(7)·10^(2)}.Weak antiferromagnetic(AFM)coupling between the adjacent RE ions for all the present complexes was found according to the magnetic *** observed significant cryogenic magnetocaloric effect(MCE)with the maximum magnetic entropy change-ΔS_(M)^(max) to be 26.3 J/(kg·K)withΔH=7 T in Gd_(2)(L)_(2)(DMF)_(4) complex makes it competitive for the cryogenic magnetic ***,the slow magnetic relaxation behavior at 0.2 T dc field with an obvious large U_(eff)/k=45(4)K and τ_(0)=6.5(2)×10^(-10)s was confirmed in Dy_(2)(L)_(2)(DMF)_(4)*** work not only provides an effective strategy for obtaining molecular materials with high MCE,but also confirms that tricarboxylate ligands are the ideal choice for constructing stable high dimensional geometric structures.

关键词： magnetocaloric effect Rare earth based complex Magnetic properties Slow magnetic relaxation bahavior

magnetocaloric effect of (Gd_(1-x)Ce_x)Co_2 compounds in low magnetic fields

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Rare Metals 2009年第5期28卷 487-490页

作者： CHEN Xiang ZHUANG Yinghong FANG Fei YAN Jialin Department of Physics and Electronic Informational Engineering Neijiang Teachers College Neijiang 641002 China Key laboratory of Nonferrous Metal Materials and New Processing Technology Ministry of Education Guangxi University Nanning 530004 China

The phases in the compounds （Gd1-xCex）Co2 with x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 were investigated by X-ray diffraction, and the magnetocaloric effect for x = 0-0.4 was studied by magnetization measurements. The samples are almost single phase with a cubic MgCu2-type structure for x = 0-0.5. The magnetization decreases with an increase in Ce content. There is almost no magnetic transition for x = 0.5 at 100-350 K. The Curie temperature （To） of the （Gd1-xCex）Co2compounds with x from 0.1 to 0.4 are 350, 344, 340, and 338 K respectively. The maximum magnetic entropy change is 2.34 J·kg^-1·K^-1 when x = 0.3. The results of Arrott plots show that the magnetic phase transition is second-order magnetic phase transition in these compounds.

关键词： magnetic refrigeration materials magnetocaloric effect X-ray diffraction magnetic entropy change

magnetocaloric effect of (Gd_(1-x)Nd_x)Co_2 alloys in low magnetic field

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Rare Metals 2008年第4期27卷 350-353页

作者： CHEN Xiang ZHUANG Yinghong YAN Jialin ZHOU Kaiwen LI Kefeng Key laboratory of the Ministry of Education of China for Nonferrous Metal Materials and New Processing Technology Guangxi University Nanning 530004 China Department of Physics and Electronic Informational Engineering Neijiang Teachers College Neijiang 641002 China

The phases and magnetocaloric effect in the alloys （Gd1-xNdx）Co2 with x = 0, 0.1, 0.2, 0.3, and 0.4 were investigated by X-ray diffraction analysis and magnetization measurement. The samples are single phase with a cubic MgCu2-type structure. The To decreases obviously with increasing Nd content from 404 K of the alloy with x = 0 to 272 K of the alloy with x = 0.4; forx = 0.3, the To is 296 K, which is near room temperature. In the samples （Gd1-xNdx）Co2 with x = 0.0, 0.1, 0.2, 0.3, and 0.4, the maximum magnetic entropy change is 1.471, 1.228, 1.280, 1.381 and 1.610 J·kg^-1·K^-1, respectively, in the applied field range of 0-2.0 T. The results of Arrott plots confirmed that the transition type were second order magnetic transition forx = 0, 0.3, and 0.4.

关键词： magnetic refrigeration materials magnetocaloric effect magnetic entropy change phase transition

magnetocaloric effect in Colossal Magnetoresistance Material (La_(0.6)Dy_(0.1))Sr_(0.3)MnO_3

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Journal of Rare Earths 2005年第1期23卷 59-62页

作者：蔡之让徐素军刘宁孙勇童伟张裕恒 CMR Materials Research Laboratory Suzhou College Suzhou 234000 China Structure Research Laboratory University of Science and Technology of China Hefei 230026 China

The magnetocaloric effect in the A-site doping colossal magnetoresistance material (La_(0.6)Dy_(0.1))Sr_(0.3)MnO_3 was studied. From the measurement and calculation of isothermal magnetization (M-H) curves under various temperatures, a large magnetocaloric effect with ferromagnetic-paramagnetic transition, additional magnetism exchange action introduces additional magnetic entropy change was discovered. This result suggests that (La_(0.6)Dy_(0.1))Sr_(0.3)MnO_3 is a suitable candidate as working substance at room temperature in magnetic refrigeration technology.

关键词： magnetic refrigeration magnetocaloric effect magnetic entropy change Curie temperature rare earths

magnetocaloric effect of Pr_2Fe_(17-x)Mn_x alloys

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Rare Metals 2014年第5期33卷 552-555页

作者： Xi-Chun Zhong Zhong-Wu Liu De-Chang Zeng Karl A.Gschneidner Jr. Vitalij K.Pecharsky School of Materials Science and Engineering South China University of Technology Ames Laboratory U.S.Department of Energy and Department of Materials Science and Engineering Iowa State University

Polycrystalline Pr2Fe17-xMnx（x = 0, 1, and 2）alloys were studied by X-ray diffraction（XRD）, heat capacity, ac susceptibility, and isothermal magnetization measurements. All the alloys adopt the rhombohedral Th2Zn17-type structure. The Curie temperature increases from 283 K at x = 0 to 294 K at x = 1, and then decreases to 285 K at x = 2. The magnetic phase transition at the Curie temperature is a typical second-order paramagnetic–ferromagnetic transition. For an applied field change from0 to 5 T, the maximum-△SM for Pr2Fe17-xMnxalloys with x = 0, 1, and 2 are 5.66, 5.07, and 4.31 J·kg^-1·K^-1,respectively. The refrigerant capacity（RC） values range from 458 to 364 J·kg^-1, which is about 70 %–89 % that of Gd. The large, near room temperature △SM and RC values,chemical stability, and a high performance-to-cost ratio make Pr2Fe17-xMnxalloys be selectable materials for room temperature magnetic refrigeration applications.

关键词： Pr2Fe17-xMnx alloys magnetocaloric effect Magnetic entropy change

magnetocaloric effect of Alloys Gd(Al_(1-x)Co_x)_2

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Journal of Rare Earths 2007年第6期25卷 783-786页

作者：邓健秋祝金明严嘉琳庄应烘王日初 School of Materials Science and Engineering Central South University Key Laboratory of New Processing Technology for Nonferrous Metal and Materials Ministry of Education Guangxi University

The magnetocaloric effect in alloys Gd（Al1-xCox）2 with x = 0, 0.05, and 0.10 were investigated using X-ray diffraction （XRD） and magnetization measurements. It was found that three alloys crystallized in a single phase with MgCu2-type structure. The lattice parameter and Curie temperature decreased with increasing Co content, whereas the magnetic-entropy change increased. With a magnetic-field change of 2 T, the maximum of the magnetic-entropy change reached 4.6 J·kg^-1·K^-1 near Curie temperature at approximately 95 K in the alloy GdAl1.8Co0.2, which appeared to be an alternative candidate for active magnetic refrigerants working in the temperature range centered at 100 K.

关键词： GdAl2 magnetocaloric effect rare earth alloy

magnetocaloric effect of(Tb_(1-x)Ce_x)Co_2 alloys in low magnetic field

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Journal of Rare Earths 2009年第6期27卷 1027-1030页

作者：陈湘庄应烘 Key Laboratory of Nonferrous Metal Materials and New Processing Technology Guangxi University Department of Physics and Electronic Informational Engineering Neijiang Teachers College

The phases in alloys(Tb1–xCex)Co2 with x=0,0.1,0.2,0.3,0.4 and 0.5 were investigated by X-ray diffraction analysis,and the magnetocaloric effect for x=0–0.4 was studied by magnetization *** samples were almost single phase with MgCu2-type cubic *** magnetization decreased with the increase of *** Curie temperatures(Tc) of Tb1–xCexCo2 alloys with x from 0.1 to 0.4 were 180,165,160 and 152 K,*** x=0.5 in the range from 100 K to 230 K,the point of magnetic transition was n...

关键词： RECo2 alloy crystal structure magnetocaloric effect X-ray diffraction rare earths

magnetocaloric effect and magnetic properties of La_(0.9)Ce_(0.1)(Fe_(0.99)Mn_(0.01))_(11.6)Si_(1.4)H_(1.6) compound

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Journal of Rare Earths 2011年第5期29卷 474-476页

作者：王超伦龙毅马涛张虎 School of Materials Science and Engineering University of Science and Technology Beijing

magnetocaloric effect and magnetic properties of La0.9Ce0.1（Fe0.99Mn0.01）11.6Si1.4 and its hydride La0.9Ce0.1（Fe0.99Mn0.01）11.6Si1.4H1.6 were investigated. The Curie temperature of La0.9Ce0.1（Fe0.99Mn0.01）11.6Si1.4 was increased by hydrogen absorption. XRD patterns showed that the structure of La0.9Ce0.1（Fe0.99Mn0.01）11.6Si1.4H1.6 remained NaZn13-type. The Curie temperature （TC） of the sample was increased from 174 K to 331 K. The homogeneity of the hydrogen absorption for La0.9Ce0.1（Fe0.99Mn0.01）11.6Si1.4H1.6 was proven very well by the random measurement of DSC. The magnetic entropy △SM of La0.9Ce0.1（Fe0.99Mn0.01）11.6Si1.4H1.6 had peak at 326 K. The peak value of-△SM-was 12.3 and 7.8 J/（kg.K） under magnetic field change of 0–2 T and 0–1 T,respectively,which was comparable with Gd5Si2Ge2. The negative slope and inflection point of the Arrott curve indicated that the first-order magnetic transition of La0.9Ce0.1（Fe0.99Mn0.01）11.6Si1.4 was reserved after hydrogen absorption.

关键词： homogeneity of hydrogen absorption magnetocaloric effect magnetic entropy change rare earths