Phenomenological crystal-field model of the magnetic and thermal properties of the Kondo-like system UCu2Si2

Abstract

The transport properties described previously [Tro\ifmmode \acute{c}\else \'{c}\fi{} et al., Phys. Rev. B 85, 224434 (2012)] as well as the magnetic and thermal properties presented in this paper, observed for single-crystalline UCu${}_{2}$Si${}_{2}$, are discussed by assuming a dual (localized-itinerant) scenario. The electronic states of the localized 5$f$ electrons in UCu${}_{2}$Si${}_{2}$ are constructed using the effective Hamiltonian known for ionic systems, allowing us to treat the Coulomb, spin-orbital, and crystal-field interactions on equal footing. The space of parameters has been restricted in the initial steps with the aid of the angular overlap model approximation. The final crystal-field parameters, obtained from the refined steps of calculations, are relatively large (in absolute values), which we attribute to the hybridization characteristic of the metallic systems on the verge of localization. The proposed crystal-field model reproduces correctly with satisfactory accuracy the magnetic and thermal properties of UCu${}_{2}$Si${}_{2}$ in agreement also with the transport properties reported previously. Considerable crystal-field splitting of the ground multiplet of 2760 K is responsible for a large anisotropy in the magnetic behavior, observed in the whole temperature range explored.