Quasiquartet CEF ground state with possible quadrupolar ordering in the tetragonal compound YbRu$_{2}$Ge$_{2}$

H. S. Jeevan; Z. Hossain; C. Geibel

doi:10.1103/PhysRevB.73.020407

paper

Quasiquartet CEF ground state with possible quadrupolar ordering in the tetragonal compound YbRu $_{2}$ Ge $_{2}$

arXiv:cond-mat/0512527 · doi:10.1103/PhysRevB.73.020407

Abstract

e have investigated the magnetic properties of YbRu $_{2}$ Ge $_{2}$ by means of magnetic susceptibility $χ$ (T), specific heat C(T) and electrical resistivity $ρ$ (T) measurements performed on flux grown single crystals. The Curie-Weiss behavior of $χ$ (T) along the easy plane, the large magnetic entropy at low temperatures and the weak Kondo like increase in $ρ$ (T) proves a stable trivalent Yb state. Anomalies in C(T), $ρ$ (T) and $χ$ (T) at T $_{0}$ = 10.2 K, T $_{1}$ = 6.5 K and T $_{2}$ = 5.7 K evidence complex ordering phenomena, T $_{0}$ being larger than the highest Yb magnetic ordering temperature found up to now. The magnetic entropy just above T $_{0}$ amounts to almost Rln4, indicating that the crystal electric field (CEF) ground state is a quasiquartet instead of the expected doublet. The behavior at T $_{0}$ is rather unusual and suggest that this transition is related to quadrupolar ordering, being a consequence of the CEF quasiquartet ground state. The combination of a quasiquartet CEF ground state, a high ordering temperature, and the relevance of quadrupolar interactions makes YbRu $_{2}$ Ge $_{2}$ a rather unique system among Yb based compounds.

arXiv comment11 pages, 5 figure, submitted to PRB rapid

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Hall-effect evolution across a heavy-fermion quantum critical point

Quasiquartet CEF ground state with possible quadrupolar ordering in the tetragonal compound YbRu2​Ge2​

Abstract

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Quasiquartet CEF ground state with possible quadrupolar ordering in the tetragonal compound YbRu $_{2}$ Ge $_{2}$