Regensburg 2002 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 17: Postersitzung II: Mesoskopische Systeme (1-19), Supraleiter: Theorie (20-26), Elektronenstruktur, Phononen, Tunneln, Ordnungsparameter (27-33), Schwere Fermionen, Kondo-Systeme (34-45)
TT 17.26: Poster
Mittwoch, 13. März 2002, 14:30–18:00, A
Structural and physical properties of new rare earth containing RE2Ni15P15, RE=La, Ce, Pr — •A. Bentien, S. Budnyk, S. Paschen, M. Baenitz, Yu. Grin, and F. Steglich — MPI für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, D - 01187 Dresden
New rare earth containing phases have been synthesized with the composition RE2Ni36P15, RE=La, Ce, Pr, the compounds crystallize in a new structure type with an orthogonal unit cell. Despite a rather complex structure there is only one RE site. The rare-atoms are encapsulated in a relatively small cage, made from Ni and P atoms. Two such share one large face, so that the shortest RE-RE distance is approximately 4.2 Å. The measurements of susceptibility, specific heat and resistivity are carried out to probe the ground state and to search for Kondo-insulator-like behavior. Indeed both the Ce and Pr compounds show features at low temperatures that are different from the La reference compound. Two maxima in the difference specific heat are observed at 3.4 K and 60 K (Pr), 1.1 K and 39 K (Ce), but the measurement of susceptibility and resistivity indicate no magnetic ordering. For the Pr compound the maxima have a characteristic Schottky anomaly shape and subsequent modeling of the specific heat data supports that the maxima in Pr are due to crystal field splitting. Furthermore the Ce compound shows a Kondo like minima in the resistance. At 2K negative magneto resistance, characteristic for Kondo systems above the coherence temperature (but also for magnetically ordered systems above the ordering temperature) is observed. Future measurements will reveal whether this compound is a Kondo system or if it orders magnetically.