Site-Preferential Design of Itinerant Ferromagnetic Borides: Experimental and Theoretical Investigation of MRh6B3 (M = Fe, Co)

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• 作者：Patrick R. N. Misse ; Michael Gille脽en ; Boniface P. T. Fokwa
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：October 17, 2011
• 年：2011
• 卷：50
• 期：20
• 页码：10303-10309
• 全文大小：927K
• 年卷期：v.50,no.20(October 17, 2011)
• ISSN：1520-510X

文摘

Single-phase polycrystalline samples of the compounds MRh₆B₃ (M = Fe, Co) as well as single crystals of CoRh₆B₃ have been synthesized by arc-melting the elements under a purified argon atmosphere in a water-cooled copper crucible. The characterization of the new phases was achieved by using single-crystal and powder X-ray diffraction as well as EDX measurements. The two phases are isotypic and crystallize in the hexagonal Th₇Fe₃ structure type (space group P6₃mc, no. 186, Z = 2). In this structure, the magnetically active atoms (Fe, Co) are preferentially found on only one of the three available rhodium sites, and together with rhodium they build a three-dimensional network of interconnected (Rh/M)₃ triangles. Magnetic properties investigations show that both phases order ferromagnetically below Curie temperatures of 240 K (for FeRh₆B₃) and 150 K (for CoRh₆B₃). First-principles DFT calculations correctly reproduce not only the lattice parameters but also the ground state magnetic ordering in the two phases. These calculations also show that the long-range magnetic ordering in both phases occurs via indirect ferromagnetic coupling between the iron atoms mediated by rhodium. This magnetic structural model also predicts the saturation magnetizations to be 4.02 渭_B for FeRh₆B₃ (3.60 渭_B found experimentally) and 2.75 渭_B for CoRh₆B₃. Furthermore, both phases are predicted to be metallic conductors as expected for these intermetallic borides.