W. Trinkl

Heavy fermions in LiV2O4: Kondo compensation versus geometric frustration

7Li nuclear magnetic resonance and heat capacity measurements were performed on the metallic spinel LiV2O4 down to 30 mK. The temperature dependencies of the linewidth, the Knight shift and the spin-lattice relaxation rate were investigated in the temperature range 30 mK≤T≤280 K and at applied magnetic fields of 4.6, 10, 44 and 83 kOe. The longitudinal nuclear magnetization was found to relax following a stretched-exponential form with a stretching exponent in the range 0.5<β<1. For temperatures T<1 K and at the lowest applied magnetic field of 4.6 kOe, we observe a spin-lattice relaxation rate which slows down exponentially, exhibiting a hindering barrier of the order of 1 K. This excitation energy separates different configurations of a highly degenerate ground state of a completely frustrated magnet.

MAGNETIC PROPERTIES OF THE SPIN GLASS PRAU2SI2

Abstract We examined the magnetic properties of pure PrAu2Si2 and present results of linear and nonlinear magnetic susceptibility measurements. The data show the characteristic features of a canonical spin glass, e.g. the critical behavior of the nonlinear susceptibility at the glass transition and the frequency dependence of the complex linear susceptibility near the freezing temperature, which is determined near T F ≈3 K . It is the first time that spin glass behavior was found in a pure rare-earth compound with well-localized magnetic moments.

Ground state properties of Ce(Pd1−xNix)2Ge2 and CeNi2(Ge1−ySiy)2

Abstract We present the results of a systematic study of transport, magnetic and calorimetric properties of the Kondo–lattice compounds Ce(Pd 1− x Ni x ) 2 Ge 2 and CeNi 2 (Ge 1− y Si y ) 2 . Due to the substitution of Pd by Ni and Ge by Si the hybridization strength changes continously, yielding a transition from local moment magnetism to intermediate valence behavior. Special attention is given to the regime where the magnetic order is suppressed characterized by significant deviations from Fermi-liquid behavior.