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

TL;DR

This study investigates In-doped YMn2Zn20, a pyrochlore lattice compound, revealing heavy-fermion-like behavior driven by geometrical frustration rather than Kondo effect, with no magnetic long-range order down to 0.4 K.

Contribution

It demonstrates that geometrical frustration in a pyrochlore lattice can induce heavy-fermion-like behavior without Kondo effect, expanding understanding of strongly correlated electron systems.

Findings

No magnetic long-range order down to 0.4 K.

Spin-glass transitions observed in In-rich crystals.

Large heat capacity indicating heavy-fermion-like behavior.

Abstract

We report on a ternary intermetallic compound, "YMn2Zn20", comprising a pyrochlore lattice made of Mn atoms. A series of In-doped single crystals undergo no magnetic long-range order down to 0.4 K, in spite of the fact that the Mn atom carries a local magnetic moment at high temperatures, showing Curie-Weiss magnetism. However, In-rich crystals exhibit spin-glass transitions at approximately 10 K due to a disorder arising from the substitution, while, with decreasing In content, the spin-glass transition temperature is reduced to 1 K. Then, heat capacity divided by temperature approaches a large value of 280 mJ K-2 mol-1, suggesting a significantly large mass enhancement for conduction electrons. This heavy-fermion-like behavior is not induced by the Kondo effect as in ordinary f-electron compounds, but by an alternative mechanism related to the geometrical frustration on the pyrochlore lattice, as in (Y,Sc)Mn2 and LiV2O4, which may allow spin entropy to survive down to low temperatures and to couple with conduction electrons.