Regensburg 2013 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

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

TT 59.2: Vortrag

Donnerstag, 14. März 2013, 15:15–15:30, H6

µSR investigations on the 4f-derived ferromagnetic quantum quantum critical system YbNi₄(P_1−xAs_x)₂ — •Rajib Sarkar¹, Johannes Spehling¹, Cornelius Krellner², Hubertus Luetkens³, Chris Baines³, Manuel Brando⁴, Christoph Geibel⁴, and Hans-Henning Klauss¹ — ¹IFP, TU Dresden, D-01069 Dresden, Germany — ²Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany — ³PSI, CH-5232 Villigen PSI, Switzerland — ⁴MPI-CPFS, D-01187 Dresden, Germany

Ferromagnetic quantum criticality (FMQC) is one central topic of research in strongly correlated electron systems. Despite adequate research so far there is no concrete evidence of FMQC. In this context, the recently discovered 4f-derived heavy fermion FM metal YbNi₄P₂ with T_c =170 mK, a Kondo temperature T_K=8 K and a very small ordered moment of ≈ 0.05 µ_B, deserves particular interest [1]. With 8 % As substitution at the P site, T_c goes down to 28 mK and the Grüneisen ratio diverges as Γ(T)∝ T^−0.22, evidencing the presence of FMQC. For YbNi₄P₂, zero field µSR investigations prove static long range magnetic ordering [2] and the ordered moment is strongly suppressed with increasing As-substitution. For 8% As, µSR time spectra suggest that static ordering appears below 20 mK. Here, we present our recent µSR results for x ≤ 0.13 and discuss the dynamics of the quantum fluctutations at this ferromagnetic quantum critical point.
[1] New J. Phys. 13, 103014 (2011)
Phys. Rev. B 85, 140406 (2012)