Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 8: Correlated Electrons: Heavy Fermions
TT 8.4: Vortrag
Montag, 27. März 2006, 15:15–15:30, HSZ 301
The role of geometrical frustration in YbInCu4, where In is substituted with Cd or Rh — •Veronika Fritsch1,2, Joe D. Thompson1, and John L. Sarrao1 — 1Los Alamos National Laboratory, Los Alamos, NM 87545, USA — 2Physikalisches Institut, Universität Karlsruhe, D-76128 Karlsruhe, Germany
YbInCu4, which is well-known for its unique first-order valence transition, crystallizes in the cubic AuBe5-structure, as do all compounds RInCu4 with R = Gd - Lu. In this structure the magnetic rare-earth ions are located on a fcc-lattice and therefore form networks of tetrahedra. Geometrical frustration of magnetism was discovered in the compounds RInCu4 (R = Gd - Tm)[1]. Substitution of In in RInCu4 with Cd increases the electrical conductivity significantly and therefore destroys the frustration. The high-temperature phase of YbInCu4 is equivalent to the frustrated RInCu4 compounds: the localized magnetic moments of the Yb form a fcc-lattice. However, the frustration found in the other RInCu4 compounds can not be found in YbInCu4 at low temperatures due to the valence transition destroying the localized magnetic moment. Substituting In with Cd or Rh initially raises the temperature of the valence transition and subsequently suppresses it. While Cd-substitution not only suppresses the valence transition but also the frustration due to enhancement of conductivity, Rh-substitution preserves the low electrical conductivity. Here we present measurements of the magnetic and transport properties of the two series YbIn1−xCdxCu4 and YbIn1−xRhxCu4 and discuss the role of geometrical frustration in both systems.
[1] V. Fritsch et al., Phys. Rev. B 71, 132402, (2005)