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TT: Fachverband Tiefe Temperaturen

TT 4: CE: Quantum-Critical Phenomena 1

TT 4.4: Vortrag

Montag, 14. März 2011, 11:15–11:30, HSZ 201

Incipient quantum criticality in single-crystal Fe₂TiSn — A. Neubauer¹, •M. Wagner¹, M. Schulz^1,2, A. Senyshyn², K. Hradil^2,3, R. Korntner¹, A. Bauer¹, S. Gottlieb-Schönmeyer¹, R. Jungwirth², G. Behr⁴, J. Kübler⁵, C. Felser⁶, and C. Pfleiderer¹ — ¹Physik-Department, TU München, 85748 Garching — ²FRM II, TU München, 85748 Garching — ³Institut für physikalische Chemie, U Göttingen, 37077 Göttingen — ⁴IFW Dresden, 01171 Dresden — ⁵Institut für Festkörperphysik, TU Darmstadt, 64289 Darmstadt — ⁶Institut für Anorganische und Analytische Chemie, U Mainz, 55099 Mainz

We have grown single-crystals of the Heusler compound Fe₂TiSn by optical float-zoning. Two parasitic effects, notably the formation of an impurity phase and surface segregations, account for the ferromagnetic (FM) properties of polycrystals of Fe₂TiSn previously attributed to atomic site interchanges. A detailed structural characterization establishes that our single crystals are phase-pure with a typical abundance of twinning domains and a trend to split site disorder of the Fe and Ti atoms. In phase-pure single crystals the temperature dependence of the susceptibility and specific heat suggest incipient FM quantum criticality, masked below a few K by a weak spin-glass transition. With decreasing temperature the resistivity increases characteristic of a small charge gap. The Hall effect corresponds to a charge carrier concentration n_H≈ 10²² cm⁻³ with an additional anomalous magnetic field dependence. Compared to conventional scenarios of FM quantum criticality the properties of Fe₂TiSn differ in a number of surprising ways.