Electrical and Magnetic Properties of R_3Al_<11> (R=La, Ce, Pr, and Nd)(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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High-quality single crystals of R_3Al_<11> (R=La, Ce, Pr, and Nd) with the La_3A_<11>-type orthorhombic crystal structure (space group Immm) have been grown by the Al-flux method. For Ce_3Al_<11>, signatures for ferromagnetic and antiferromagnetic orderings at T_C=6.3K and T_N=3.2K, respectively, have been observed in the magnetic susceptibility, magnetization, specific heat, and electrical resistivity. An antiferromagnet Pr_3Al_<11>, on the other hand, exhibits two magnetic transitions at T_<N1>=12.6K and T_<N2>=3.1K. An antiferromagnet Nd_3Al_<11>also exhibits multiple magnetic transitions at T_<N1>=13.2K, T_<N2>=9.4K, T_<N3>=2.9K, and T_<N4>=1.77K in zero magnetic field. The transition at T_<N4> has a first-order character. The crystalline electric field (CEF) analysis of magnetic susceptibility, magnetization and specific heat data shows that the CEF splitting is larger for Ce_3Al_<11>than for Pr_3Al_<11> and Nd_3Al_<11>. The CEF ground state of Pr_3Al_<11> is a singlet. Magnetic order occurs in this compound owing to the exchange mixing of the CEF ground state and low-lying excited states. The ferromagnetic like component of the magnetization for H ‖ [010] is characteristic of R_3Al_<11> (R=Ce, Pr, and Nd), which is most likely due to the Dzialoshinsky-Moriya interaction for two nonequivalent R atoms.
社団法人日本物理学会の論文
2008-12-15