Neutron scattering and scaling behavior in URu_ {2} Zn_ {20} and YbFe_ {2} Zn_ {20}

Physical Review B (Impact Factor: 3.74). 11/2010; 82(18). DOI: 10.1103/PhysRevB.82.184407
Source: arXiv


The dynamic susceptibility χ″(ΔE), measured by inelastic neutron-scattering measurements, shows a broad peak centered at Emax=15 meV for the cubic actinide compound URu2Zn20 and 7 meV at zone center and at the (1/2, 1/2, 1/2) zone boundary for the rare-earth counterpart compound YbFe2Zn20. For URu2Zn20, the low-temperature susceptibility and magnetic specific-heat coefficient γ=Cmag/T take the values χ=0.011 emu/mole and γ=190 mJ/mole K2 at T=2 K. These values are roughly three times smaller, and Emax is three times larger, than recently reported for the related compound UCo2Zn20, so that χ and γ scale inversely with the characteristic energy for spin fluctuations, Tsf=Emax/kB. While χ(T), Cmag(T), and Emax of the 4f compound YbFe2Zn20 are very well described by the Kondo impurity model, we show that the model works poorly for URu2Zn20 and UCo2Zn20, suggesting that the scaling behavior of the actinide compounds arises from spin fluctuations of itinerant 5f electrons.

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