Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 8: Correlated Electrons: Heavy Fermions
TT 8.6: Vortrag
Montag, 27. März 2006, 15:45–16:00, HSZ 301
Field-induced enhancement of the linear static susceptibility in heavy-fermion YbAgGe — •P. G. Niklowitz1,2, C. Paulsen3, S. L. Budko4, P. C. Canfield4, and J. Flouquet1 — 1DRFMC/SPSMS/CEA-Grenoble, F-38054 Grenoble Cedex 9, France — 2Physik Department, E21, Technische Universität München, James-Franck-Str., D-85748 Garching — 3CRTBT/CNRS, BP 166, F-38042 Grenoble Cedex 9 — 4Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
Hexagonal YbAgGe is a recently discovered heavy-fermion (HF) system with TK≈ 25 K, γ of a few hundred mJ/molK2 and planar magnetic anisotropy χab/χc≈ 3 at low temperatures. Two antiferromagnetic phases AF1 and AF2, become fully suppressed with fields Hc1=1.9 T and Hc2=3.0 T, when the field is applied in the ab-plane. Furthermore, there are indications for a transition or crossover at a field Hc3=4.9 T and low-T resistivity measurements suggest a strong enhancement of thermally excited fluctuations close to Hc3. The resistivity is non-Fermi-liquid (NFL) like close to Hc3. We have now measured the magnetisation of single crystals of YbAgGe up to 8 T and down to 50 mK with the field applied along the a-axis. The results confirm the first-order character of the transition between the AF1 and AF2 phase. No clear signature of the suppression of the AF2 phase is found. However, the static linear susceptibility becomes enhanced when approaching Hc3, especially at the lowest temperatures. This enhancement suggests that magnetic fluctuations are at the origin of field-induced NFL behaviour in YbAgGe, but that ferromagnetic fluctuations are not the only ingredient.