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TT: Fachverband Tiefe Temperaturen

TT 59: Correlated Electrons: Quantum-Critical Phenomena - Experiments

TT 59.4: Talk

Thursday, March 14, 2013, 15:45–16:00, H6

Quantum criticality in partially frustrated CePd_1−xNi_xAl — •Veronika Fritsch¹, Sarah Woitschach², Oliver Stockert², Wolfram Kittler¹, and Hilbert v. Löhneysen^1,3 — ¹Physikalisches Institut, Karlsruher Institut für Technologie (KIT), 76131 Karlsruhe, Germany — ²Max-Planck-Institut für chemische Physik fester Stoffe, Dresden, Germany — ³Institut für Festkörperphysik, Karlsruher Institut für Technologie (KIT), 76021 Karlsruhe, Germany

In the antiferromagnetic (AF) heavy-fermion system CePdAl the magnetic Ce ions form a network of equilateral triangles in the (001) plane, similar to the kagomé lattice, with one third of the Ce moments not participating in the long-range order due to geometrical frustration. The Néel temperature T_N = 2.7 K is reduced upon replacing Pd by Ni in CePd_1−xNi_xAl, with T_N → 0 for x ≈ 0.14. At this concentration the specific heat C exhibits a C/T ∝ − log T dependence. This and the linear T_N(x) dependence are indicative of two-dimensional (2D) critical AF fluctuations within the conventional description of quantum criticality after Hertz, Millis and Moriya, in marked contrast to the three-dimensional (3D) magnetic order found by neutron diffraction experiments in CePdAl. We discuss the role of frustration when approaching the quantum critical point in Ni-substituted CePdAl on the basis of measurements of the magnetization, specific heat, electrical resistivity, and neutron diffraction experiments.