Origin of Weak Ferromagnetism in Yb_xFe_4Sb_<12>, Relationship between Weak Ferromagnetism and Filling Ratio x(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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The magnetization and specific heat of single-crystalline samples of filled-skutterudite compounds Yb_x:Fe_4Sb_<12> were measured. Six single crystals with the filling ratio of Yb, x, from 0.875 to 0.910 were prepared. The weak ferromagnetism of Yb_xFe_4Sb_<12> appearing at low temperatures was found to strongly correlate with x; with increasing x from 0.875 to 0.910, the transition temperature, T_C, decreases from 17 to 5K and the weak-ferromagnetic moment, mo, decreases from 0.066 to 0.005μ_B/Fe. From these trends, both T_C and m_o were expected to reach zero at the critical concentration, x_c=0.93. In the temperature dependence of the specific heat, no anomaly at T_C was observed, reflecting that m_o is extremely small compared with the effective Bohr magneton number. With the application of pressure, the T_C of the sample with x=0.882 increases rapidly, with the ratio of dT_C/dP=+5.27K/GPa. This weak ferromagnetism of Yb_xFe_4Sb_<12> originates from the itinerant 3d electrons of Fe in anions [Fe_4Sb_<12>].
社団法人日本物理学会の論文
2007-02-15