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Regensburg 2000 – scientific programme

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TT: Tiefe Temperaturen

TT 7: Postersitzung I: Amorphe- und Tunnelsysteme (1-8), Mesoskopische Systeme (9-21), Schwere Fermionen (22-32), Kernmagnetismus (33-34), Josephson-Kontakte und SQUIDs (35-45), TT-Detektoren und Kryotechnik (46-49)

TT 7.30: Poster

Monday, March 27, 2000, 14:30–18:00, A

Magnetic Behaviour of the New Kondo Lattice Systems Ce2M3Ge5 (M = Rh, Ir, Ni) — •Z. Hossain1, S. Hamashima2, K. Umeo2, and T. Takabatake21Max-Planck-Institut für Chemische Physik fester Stoffe, Bayreuther Str. 40, 01187 Dresden — 2Department of Quantum Matter, ADSM, Hiroshima University, 739 8526 Japan

We report physical properties of Ce2M3Ge5 (M = Rh, Ir, Ni). Occurrence of peaks in the susceptibility and heat capacity suggests Ce2M3Ge5 (Rh, Ir) undergo antiferromagnetic ordering below TN 5.5 K and 9.5 K, respectively. Ce2Ni3Ge5 shows two magnetic transitions at 4.5 K and 5.1 K. The magnetic contribution to the resistivity varies as -lnT in two distinct temperature regions. This type of behavior is suggestive of Kondo effect in presence of crystal field effect. A very large drop in resistivity below TN in Ce2Rh3Ge5 and Ce2Ir3Ge5 is attributed to the combined effect of the decrease in the spin disorder scattering and development of coherence in the Kondo Lattice. The temperature dependence of resistivity and specific heat below 4 K reveal the appearance of spin wave-gap in Ce2Ni3Ge5. The magnetic entropy at TN reaches 0.5Rln2, 0.65Rln2 and 0.65Rln2 for Rh, Ir and Ni compounds respectively, which suggest that the ground state is a doublet and there is a considerable reduction of the magnetic moments due to presence of Kondo effect. The large value of linear coefficient of the heat capacity ( 150 mJ/mol Ce K2) for Ce2M3Ge5 ( M = Rh, Ir) suggests that they are moderate heavy fermion compounds. The Kondo temperatures are in the range 5-10 K. The magnetoresistance in the paramagnetic region is negative which is characteristic of the Kondo effect.

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