The compound ingots of Pr0.15TbxDy0.85-xFe2 (x=0 to 0.85) were prepared by arc melting in a water Cu boat using arc furnace under a purified Ar atmosphere. Appropriate annealing (850℃, 100 h) can obtain single Laves ...The compound ingots of Pr0.15TbxDy0.85-xFe2 (x=0 to 0.85) were prepared by arc melting in a water Cu boat using arc furnace under a purified Ar atmosphere. Appropriate annealing (850℃, 100 h) can obtain single Laves phase compound. The magnetostriction for these systems will rise obviously when partially substituted Tb or Dy by Pr.展开更多
The structural and magnetostrictive properties of (CexTb1-x)0.5Pr0.5Fe_2 were investigated. Ceconcentration must exceed x=0.6 in order to obtain the pure Laves phase. The magnetostriction and anisotropy constant incr...The structural and magnetostrictive properties of (CexTb1-x)0.5Pr0.5Fe_2 were investigated. Ceconcentration must exceed x=0.6 in order to obtain the pure Laves phase. The magnetostriction and anisotropy constant increase with the Tb-content in this system. The anisotropy value of PrFe_2 is lower than that of isostructural DyFe_2. From the X-ray step-scanned data we found that λ_111 of PrFe_2 is 1310x10^-6. A large increase of magnetostriction can be observed under a small prestress of 6 MP_a for Ce_0.5Pr_0.5Fe_2.展开更多
The melting behavior,solid state phase transformation and structure of pseudo-ternary compounds Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B were studied using differential thermal analysis,optical microscopy...The melting behavior,solid state phase transformation and structure of pseudo-ternary compounds Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B were studied using differential thermal analysis,optical microscopy X-ray diffraction,and electron probe micro-analysis techniques.At high temperature,eutectoid decomposition R_2(Ni,M)_(17)→R(Ni,M)_5+x-Ni(M) takes place in these two pseudo-ternary compounds,in the composition range x=0.6～1.0 and y=0.3～1.0,respectively.When x(or y)≤0.2,both Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B are single phase tetragonal.The phase constitutents of these two systems at room tempera- ture are similar in the composition range 0.6≤x(or y)≤1.0.展开更多
The electronic structure of iron-pnictide compound superconductor Ba_2Ti_2Fe_2As_4O, which has metallic intermediate Ti_2O layers, is studied using angle-resolved photoemission spectroscopy. The Ti-related bands show ...The electronic structure of iron-pnictide compound superconductor Ba_2Ti_2Fe_2As_4O, which has metallic intermediate Ti_2O layers, is studied using angle-resolved photoemission spectroscopy. The Ti-related bands show a‘peak-dip-hump＇ line shape with two branches of dispersion associated with the polaronic states at temperatures below around 120 K. This change in the spectra occurs along with the resistivity anomaly that was not clearly understood in a previous study. Moreover, an energy gap induced by the superconducting proximity effect opens in the polaronic bands at temperatures below T_c（~21 K）. Our study provides the spectroscopic evidence that superconductivity coexists with polarons in the same bands near the Fermi level, which provides a suitable platform to study interactions between charge, lattice and spin freedoms in a correlated system.展开更多
The temperature dependent magnetization of the (Ce,Nd) 2(Fe,Si,Mn) 17 intermetallic compounds were measured and analyzed by molecular field theory (MFT). The relationship between T C and the intrasublattic...The temperature dependent magnetization of the (Ce,Nd) 2(Fe,Si,Mn) 17 intermetallic compounds were measured and analyzed by molecular field theory (MFT). The relationship between T C and the intrasublattice coupling interactions was discussed. The two sublattice MFT model can well describe the temperature dependence of the magnetization for all the compounds investigated. Ce ion in (Ce,Nd) 2Fe 17 compounds does not simply dilute the magnetic structure, but is likely present in a mixed valence state. The substitution of Si for Fe strongly raises T C and the mean Fe moment remains unchanged for Ce 2(Si,Fe) 17 compounds, and the 3d exchange coupling constant J FF increases linearly. Mn decreases T C of Nd 2(Mn, Fe) 17 compound by reducing J FF .展开更多
The structural and magnetic properties of Tb2Fe15CF2 compound were investigated by means of X-ray diffraction and magnetization measurements. Tb2Fe15Cr2 compound has a hexagonal Th2Ni17-type structure. Negative therma...The structural and magnetic properties of Tb2Fe15CF2 compound were investigated by means of X-ray diffraction and magnetization measurements. Tb2Fe15Cr2 compound has a hexagonal Th2Ni17-type structure. Negative thermal expansion was found in Tb2Fe15Cr2 compound from 372 to 452 K by X-ray dilatometry. The coefficient of the average thermal expansion is α^- =-3.14×10^-5 K^-1. The magnetostrictive deformations from 292 to 450 K were calculated. The result showed that the spontaneous volume magnetostrictive deformation ms remains nearly constant with increasing temperature up to 360 K, but decreases with the further increase of temperature. The spontaneous linear magnetostrictive deformation λc along the c axis decreases with increasing temperature. The spontaneous linear magnetostrictive deformation, λa, in the basal-plane increases with increasing temperature up to 360 K, but decreases with further increasing temperature.展开更多
Thermodynamics and kinetics for the preparation of Sm2Fe17 alloys by reduction-diffusion （R-D） method in CaSm2O3-Fe System were investigated. With increasing reaction temperature, it is found that the reaction rate ...Thermodynamics and kinetics for the preparation of Sm2Fe17 alloys by reduction-diffusion （R-D） method in CaSm2O3-Fe System were investigated. With increasing reaction temperature, it is found that the reaction rate of R-D and the amount of Sm in the Sm2Fe17 alloy increase, and the increased amount at lower temperature is higher than that at higher temperature. Moreover, results from contracting core modal show that the peritectic reaction between Sm and Fe is a ratedetermined step in the whole R-D process. The apparent activation energy and the pre-exponential factor for this reaction are 73.74 kJ· mol^ -1 and 7.79 × 10^- 3 respectively.展开更多
Structural, thermal expansion, and magnetic properties of the Dy_2Fe_(16)Cr compound are investigated by means of x-ray diffraction and magnetization measurements. The Dy_2Fe_(16)Cr compound has a hexagonal Th_2Ni_(17...Structural, thermal expansion, and magnetic properties of the Dy_2Fe_(16)Cr compound are investigated by means of x-ray diffraction and magnetization measurements. The Dy_2Fe_(16)Cr compound has a hexagonal Th_2Ni_(17)-type structure. There exists a negative thermal expansion resulting from a strong spontaneous magnetostriction in the magnetic state of the Dy_2Fe_(16)Cr compound. The average thermal expansion coefficient is-0.794 × 10^(-5)/K in the temperature range 292–407 K. The spontaneous magnetostrictive deformation and the Curie temperature are discussed.展开更多
基金the Natural Science Foundation of Hebei Province 596028 and the National NaturalScience Foundation of China No.59871062.
文摘The compound ingots of Pr0.15TbxDy0.85-xFe2 (x=0 to 0.85) were prepared by arc melting in a water Cu boat using arc furnace under a purified Ar atmosphere. Appropriate annealing (850℃, 100 h) can obtain single Laves phase compound. The magnetostriction for these systems will rise obviously when partially substituted Tb or Dy by Pr.
基金Natural Science of Hebei Province!(No. 596028)National Natural Science Foundation of China!(No. 59871062).
文摘The structural and magnetostrictive properties of (CexTb1-x)0.5Pr0.5Fe_2 were investigated. Ceconcentration must exceed x=0.6 in order to obtain the pure Laves phase. The magnetostriction and anisotropy constant increase with the Tb-content in this system. The anisotropy value of PrFe_2 is lower than that of isostructural DyFe_2. From the X-ray step-scanned data we found that λ_111 of PrFe_2 is 1310x10^-6. A large increase of magnetostriction can be observed under a small prestress of 6 MP_a for Ce_0.5Pr_0.5Fe_2.
基金the National Natural Science Fundation of China.
文摘The melting behavior,solid state phase transformation and structure of pseudo-ternary compounds Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B were studied using differential thermal analysis,optical microscopy X-ray diffraction,and electron probe micro-analysis techniques.At high temperature,eutectoid decomposition R_2(Ni,M)_(17)→R(Ni,M)_5+x-Ni(M) takes place in these two pseudo-ternary compounds,in the composition range x=0.6～1.0 and y=0.3～1.0,respectively.When x(or y)≤0.2,both Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B are single phase tetragonal.The phase constitutents of these two systems at room tempera- ture are similar in the composition range 0.6≤x(or y)≤1.0.
基金Supported by the National Basic Research Program of China under Grant Nos 2013CB921700,2015CB921300 and2015CB921301the National Natural Science Foundation of China under Grant Nos 11234014,11622435,11274362,11674371 and11474340+1 种基金the National Key Research and Development Program of China under Grant Nos 2016YFA0300300,2016YFA0300600,2016YFA0401000 and 2016YFA0400902the Open Large Infrastructure Research of Chinese Academy of Sciences,and the Pioneer Hundred Talents Program(Type C)of Chinese Academy of Sciences
文摘The electronic structure of iron-pnictide compound superconductor Ba_2Ti_2Fe_2As_4O, which has metallic intermediate Ti_2O layers, is studied using angle-resolved photoemission spectroscopy. The Ti-related bands show a‘peak-dip-hump＇ line shape with two branches of dispersion associated with the polaronic states at temperatures below around 120 K. This change in the spectra occurs along with the resistivity anomaly that was not clearly understood in a previous study. Moreover, an energy gap induced by the superconducting proximity effect opens in the polaronic bands at temperatures below T_c（~21 K）. Our study provides the spectroscopic evidence that superconductivity coexists with polarons in the same bands near the Fermi level, which provides a suitable platform to study interactions between charge, lattice and spin freedoms in a correlated system.
文摘The temperature dependent magnetization of the (Ce,Nd) 2(Fe,Si,Mn) 17 intermetallic compounds were measured and analyzed by molecular field theory (MFT). The relationship between T C and the intrasublattice coupling interactions was discussed. The two sublattice MFT model can well describe the temperature dependence of the magnetization for all the compounds investigated. Ce ion in (Ce,Nd) 2Fe 17 compounds does not simply dilute the magnetic structure, but is likely present in a mixed valence state. The substitution of Si for Fe strongly raises T C and the mean Fe moment remains unchanged for Ce 2(Si,Fe) 17 compounds, and the 3d exchange coupling constant J FF increases linearly. Mn decreases T C of Nd 2(Mn, Fe) 17 compound by reducing J FF .
基金This work was financially supported by the National Natural Science Foundation of China (No. 50271022), the Excellent Young Teachers Program of MOE, China (No.1999), and the Tianjin Natural Science Foundation of China (No.043602011)
文摘The structural and magnetic properties of Tb2Fe15CF2 compound were investigated by means of X-ray diffraction and magnetization measurements. Tb2Fe15Cr2 compound has a hexagonal Th2Ni17-type structure. Negative thermal expansion was found in Tb2Fe15Cr2 compound from 372 to 452 K by X-ray dilatometry. The coefficient of the average thermal expansion is α^- =-3.14×10^-5 K^-1. The magnetostrictive deformations from 292 to 450 K were calculated. The result showed that the spontaneous volume magnetostrictive deformation ms remains nearly constant with increasing temperature up to 360 K, but decreases with the further increase of temperature. The spontaneous linear magnetostrictive deformation λc along the c axis decreases with increasing temperature. The spontaneous linear magnetostrictive deformation, λa, in the basal-plane increases with increasing temperature up to 360 K, but decreases with further increasing temperature.
文摘Thermodynamics and kinetics for the preparation of Sm2Fe17 alloys by reduction-diffusion （R-D） method in CaSm2O3-Fe System were investigated. With increasing reaction temperature, it is found that the reaction rate of R-D and the amount of Sm in the Sm2Fe17 alloy increase, and the increased amount at lower temperature is higher than that at higher temperature. Moreover, results from contracting core modal show that the peritectic reaction between Sm and Fe is a ratedetermined step in the whole R-D process. The apparent activation energy and the pre-exponential factor for this reaction are 73.74 kJ· mol^ -1 and 7.79 × 10^- 3 respectively.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50871074 and 61474082
文摘Structural, thermal expansion, and magnetic properties of the Dy_2Fe_(16)Cr compound are investigated by means of x-ray diffraction and magnetization measurements. The Dy_2Fe_(16)Cr compound has a hexagonal Th_2Ni_(17)-type structure. There exists a negative thermal expansion resulting from a strong spontaneous magnetostriction in the magnetic state of the Dy_2Fe_(16)Cr compound. The average thermal expansion coefficient is-0.794 × 10^(-5)/K in the temperature range 292–407 K. The spontaneous magnetostrictive deformation and the Curie temperature are discussed.
