Neutron scattering and scaling behavior in URu2Zn20 and YbFe2Zn20

TL;DR

This study investigates the spin fluctuation behavior in URu2Zn20 and YbFe2Zn20 using neutron scattering, revealing different scaling behaviors and suggesting itinerant 5f electron involvement in actinide compounds.

Contribution

It demonstrates that the scaling of magnetic properties in URu2Zn20 and UCo2Zn20 differs from YbFe2Zn20, indicating a distinct spin fluctuation mechanism involving itinerant 5f electrons.

Findings

Emax scales inversely with susceptibility and specific heat

Kondo impurity model fits YbFe2Zn20 but not URu2Zn20

Spin fluctuations in actinide compounds involve itinerant 5f electrons

Abstract

The dynamic susceptibility chi"(deltaE), measured by inelastic neutron scattering measurements, shows a broad peak centered at Emax = 16.5 meV for the cubic actinide compound URu2Zn20 and 7 meV 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 gamma = Cmag/T take the values chi = 0.011 emu/mole and gamma = 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 chi and gamma scale inversely with the characteristic energy for spin fluctuations, Tsf = Emax/kB. While chi(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.