Itinerant-Electron Magnet of the Pyrochlore Lattice: Indium-Doped YMn₂Zn₂₀

Abstract

We report on a ternary intermetallic compound, "YMn2Zn20", comprising a\npyrochlore lattice made of Mn atoms. A series of In-doped single crystals\nundergo no magnetic long-range order down to 0.4 K, in spite of the fact that\nthe Mn atom carries a local magnetic moment at high temperatures, showing\nCurie-Weiss magnetism. However, In-rich crystals exhibit spin-glass transitions\nat approximately 10 K due to a disorder arising from the substitution, while,\nwith decreasing In content, the spin-glass transition temperature is reduced to\n1 K. Then, heat capacity divided by temperature approaches a large value of 280\nmJ K-2 mol-1, suggesting a significantly large mass enhancement for conduction\nelectrons. This heavy-fermion-like behavior is not induced by the Kondo effect\nas in ordinary f-electron compounds, but by an alternative mechanism related to\nthe geometrical frustration on the pyrochlore lattice, as in (Y,Sc)Mn2 and\nLiV2O4, which may allow spin entropy to survive down to low temperatures and to\ncouple with conduction electrons.\n