Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 56: CE: Heavy Fermions

TT 56.8: Vortrag

Donnerstag, 17. März 2011, 18:30–18:45, HSZ 105

Magnetic Phase Diagram of CeAu₂Ge₂ — •Veronika Fritsch, Bernd Pilawa, Peter Schweiss, Peter Pfundstein, and Hilbert v. Löhneysen — Karlsruher Institut für Technologie, Physikalisches Institut, 76131 Karlsruhe, Germany

CeAu₂Ge₂ single crystals (tetragonal ThCr₂Si₂ structure) have been grown in Au-Ge flux (AGF) as well as in Sn flux (SF). X-ray powder diffraction measurements and EDX measurements indicate that in the latter case Sn atoms from the flux are incorporated in the samples, leading to a decrease of the lattice constants by ≈ 0.3 % compared to AGF samples. The magnetization M demonstrates a strong dependence of the magnetic properties on the flux employed. While the SF samples adopt simple antiferromagnetic order below 9 K, a sequence of metamagnetic transitions with increasing magnetic field in the AGF samples points towards a more complex magnetic structure for B || c. One the basis of the neutron scattering data of Loidl et al. (PRB 46, 9341, 1992) we calculated the field-dependence of the magnetization at T = 20 K in the paramagnetic regime, as well as the temperature dependence, and found good agreement with our measured data for B || c and B ⊥ c. The complex phase diagram of the AGF samples in comparison to the simpler one of the SF samples is discussed within the framework of the ANNNI model, making CeAu₂Ge₂ a possible candidate for a Devil’s Staircase.