Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 17: Correlated Electrons: Quantum-Critical Phenomena 1

TT 17.2: Talk

Tuesday, March 24, 2009, 14:15–14:30, HSZ 03

Experimental Investigation of Pd_1−xNi_x at the border of Quantum Criticality — •Christian Franz¹, Christian Pfleiderer¹, Michael Schulz^1,2, Björn Pedersen², and Peter Böni¹ — ¹Physik Department E21, Technische Universität München, D-85748 Garching, Germany — ²Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universität München, D-85748 Garching, Germany

Polycrystals of the transition metal system Pd_1−xNi_x display ferromagnetic quantum criticality at a critical concentration x_c assumed to be well described by the SCR theory. We report comprehensive studies of the magnetic field and temperature dependence of the magnetization, resistivity, Hall effect and specific heat of Czochralsky grown Pd_1−xNi_x for four Ni-concentrations near x_c. Only the lowest Ni-concentration has crystallized as a single crystal, while the higher concentrations remained polycrystalline. For large values of x the typical behavior of a weakly ferromagnetic metal akin stoichiometric compounds like Ni₃Al, YNi₃ or ZrZn₂ is observed. In contrast, for low concentrations two regimes may be distinguished. Moreover, an analysis of the mode-mode coupling as inferred from the magnetic field dependence of the magnetization suggests that the it stays positive for all x as expected of quantum criticality. But the concentration dependence of the spontaneous moment indicates that Pd_1−xNi_x stays ferromagnetic on local scales even for very small concentrations. This suggests that quantum criticality in Pd_1−xNi_x is more complex then previously thought.