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TT: Fachverband Tiefe Temperaturen

TT 79: Correlated Electrons - Poster Session

TT 79.5: Poster

Mittwoch, 2. April 2014, 15:00–19:00, P2

NMR on the quantum critical ferromagnet YbNi₄P₂: Evidence for a large basal plane local anisotropy — •Rajib Sarkar¹, Marco Günter¹, Cornelius Krellner³, Christoph Geibel², and Hans-Henning Klauss¹ — ¹IFP, TU Dresden, D-01069 Dresden, Germany — ²MPI-CPFS, D-01187 Dresden, Germany — ³Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany

In the last 10 years there was growing evidence both from theoretical work and experimental observations that a ferromagnetic (FM) quantum critical point (QCP) cannot exist in a pure system, because the transition becomes first order before reaching the QCP. Therefore the recent report of clear evidence for a FM-QCP in the heavy fermion compound YbNi₄P₂ attracted considerable attention. While the Bravais lattice of this compound is tetragonal, resulting in isotropic in- plane macroscopic magnetic properties, the local symmetry on the Yb site (and on the P-site) is lower, orthorhombic. Therefore some in- plane anisotropy of local magnetic properties is expected, which could however not yet been studied because of the absence of related effects on macroscopic properties. We performed ³¹P NMR investigations on a grain aligned polycrystalline sample of YbNi₄P₂. We observed three structures in the NMR spectra, which present quite different T-dependence of the respective Knight shifts. An analysis of these results provides a clear evidence for strong local in-plane anisotropy of the Yb-moment due to the orthorhombic crystal electric field. Implication for the magnetic ordered state shall be discussed.