The reaction of Co_2(CO)_8 with EtSPCl_2 gives a new crystal like compound Co_7(μ_7-S)(μ_4-PSEt)(μ- SEt)_2(μ-CO)_2(CO)_(12),whose structure has been determined by single crystal x-ray diffraction.This special com-...The reaction of Co_2(CO)_8 with EtSPCl_2 gives a new crystal like compound Co_7(μ_7-S)(μ_4-PSEt)(μ- SEt)_2(μ-CO)_2(CO)_(12),whose structure has been determined by single crystal x-ray diffraction.This special com- pound reveals some new features in cluster chemistry^1:The fragmentation of a ligand precursor EtSPCl_2 yields three kinds of fragments,μ_7-S,μ_4-PSEt and μ-SEt,which are ligands in the same cluster molecule.There is a new type of bridging S presented——A μ_7-S atom is interspaced into seven Co core.展开更多
The crystallographic and the magnetic structures of the composite compound Nd2Co7 at 300 K are investigated by a combined refinement of X-ray diffraction data and high-resolution neutron diffraction data. The compound...The crystallographic and the magnetic structures of the composite compound Nd2Co7 at 300 K are investigated by a combined refinement of X-ray diffraction data and high-resolution neutron diffraction data. The compound crystallizes into a hexagonal Ce2NiT-type structure and consists of alternately stacking MgZn2-type NdCo2 and CaCus-type NdCo5 structural blocks along the c axis. A magnetic structure model with the moments of all atoms aligning along the c axis provides a satisfactory fitting to the neutron diffraction data and coincides with the easy magnetization direction revealed by the X-ray diffraction experiments on magnetically pre-aligned fine particles. The refinement results show that the derived atomic moments of the Co atoms vary in a range of 0.7 μB-1.1 μB and the atomic moment of Nd in the NdCo5 slab is close to the theoretical moment of a free trivalent Nd3＋ ion, whereas the atomic moment of Nd in the NdCo2 slab is much smaller than the theoretical value for a free Nd3＋ ion. The remarkable difference in the atomic moment of Nd atoms between different structural slabs at room temperature is explained in terms of the magnetic characteristics of the NdCo2 and NdCo5 compounds and the local chemical environments of the Nd atoms in different structural slabs of the Nd2Co7 compound.展开更多
(La0.5Ce0.5)2Co7 and(Ce0.65Pr0.35)2Co7 compounds for magnetic refrigeration were studied by X-ray diffraction, ac susceptibility and isothermal magnetization measurements. X-ray powder diffraction shows that all the c...(La0.5Ce0.5)2Co7 and(Ce0.65Pr0.35)2Co7 compounds for magnetic refrigeration were studied by X-ray diffraction, ac susceptibility and isothermal magnetization measurements. X-ray powder diffraction shows that all the compounds have hexagonal Ce2Ni7-type structure. The Curie temperatures(TC) are 258 K and 222 K for(La0.5Ce0.5)2Co7 and(Ce0.65Pr0.35)2Co7 compounds, respectively. High coercivities(HC) of about 1.74 and 6.61 k Oe at 5 K with a smooth demagnetization curves were obtained for the(La0.5Ce0.5)2Co7 and(Ce0.65Pr0.35)2Co7 compounds, respectively. For an applied field change from 0 to 50 k Oe, the maximum(??SM) for(La0.5Ce0.5)2Co7 and(Ce0.65Pr0.35)2Co7 compounds are 0.52 and 0.67 J/(kg K), respectively.展开更多
文摘The reaction of Co_2(CO)_8 with EtSPCl_2 gives a new crystal like compound Co_7(μ_7-S)(μ_4-PSEt)(μ- SEt)_2(μ-CO)_2(CO)_(12),whose structure has been determined by single crystal x-ray diffraction.This special com- pound reveals some new features in cluster chemistry^1:The fragmentation of a ligand precursor EtSPCl_2 yields three kinds of fragments,μ_7-S,μ_4-PSEt and μ-SEt,which are ligands in the same cluster molecule.There is a new type of bridging S presented——A μ_7-S atom is interspaced into seven Co core.
基金supported by the National Natural Science Foundation of China (Grant No. 50631040)the National Basic Research Program of China (Grants Nos. 2006CB601101 and 2006CB605101)
文摘The crystallographic and the magnetic structures of the composite compound Nd2Co7 at 300 K are investigated by a combined refinement of X-ray diffraction data and high-resolution neutron diffraction data. The compound crystallizes into a hexagonal Ce2NiT-type structure and consists of alternately stacking MgZn2-type NdCo2 and CaCus-type NdCo5 structural blocks along the c axis. A magnetic structure model with the moments of all atoms aligning along the c axis provides a satisfactory fitting to the neutron diffraction data and coincides with the easy magnetization direction revealed by the X-ray diffraction experiments on magnetically pre-aligned fine particles. The refinement results show that the derived atomic moments of the Co atoms vary in a range of 0.7 μB-1.1 μB and the atomic moment of Nd in the NdCo5 slab is close to the theoretical moment of a free trivalent Nd3＋ ion, whereas the atomic moment of Nd in the NdCo2 slab is much smaller than the theoretical value for a free Nd3＋ ion. The remarkable difference in the atomic moment of Nd atoms between different structural slabs at room temperature is explained in terms of the magnetic characteristics of the NdCo2 and NdCo5 compounds and the local chemical environments of the Nd atoms in different structural slabs of the Nd2Co7 compound.
基金supported by the U.S.Department of Energy,Office of Basic Energy Science,Division of Materials Sciences and EngineeringThe research was performed at the Ames Laboratory.Ames Laboratory is operated for the U.S.Department of Energy by Iowa State University under contract No.DE-AC02-07CH11358+2 种基金ZHONG X C also thanks the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Education Ministry of China(Grant No.x2cl B7120290)the Guangzhou Municipal Science and Technology Program(Grant No.12F582080022)the Fundamental Research Funds for the Central Universities of China(Grant Nos.2012ZZ0013 and 2014ZZ0005)
文摘(La0.5Ce0.5)2Co7 and(Ce0.65Pr0.35)2Co7 compounds for magnetic refrigeration were studied by X-ray diffraction, ac susceptibility and isothermal magnetization measurements. X-ray powder diffraction shows that all the compounds have hexagonal Ce2Ni7-type structure. The Curie temperatures(TC) are 258 K and 222 K for(La0.5Ce0.5)2Co7 and(Ce0.65Pr0.35)2Co7 compounds, respectively. High coercivities(HC) of about 1.74 and 6.61 k Oe at 5 K with a smooth demagnetization curves were obtained for the(La0.5Ce0.5)2Co7 and(Ce0.65Pr0.35)2Co7 compounds, respectively. For an applied field change from 0 to 50 k Oe, the maximum(??SM) for(La0.5Ce0.5)2Co7 and(Ce0.65Pr0.35)2Co7 compounds are 0.52 and 0.67 J/(kg K), respectively.
