Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 53: Correlated Electrons: Heavy Fermions
TT 53.11: Vortrag
Donnerstag, 14. März 2013, 12:15–12:30, H19
YbPt2Sn and YbPt2In: Unusual weak magnetic exchange in two different structure types — •Thomas Gruner, Dongjin Jang, Alexander Steppke, Manuel Brando, and Christoph Geibel — MPI Chemical Physics of Solids, 01187, Dresden, Germany
We have synthesized the two new compounds YbPt2Sn (YPS) and YbPt2In (YPI) and investigated their structural and magnetic properties. Powder diffraction patterns show YPS to crystallize in the same hexagonal ZrPt2Al structure type as previously known RPt2Sn and RPt2In (R = Y, Gd - Tm) compounds, while at 300 K YPI was found to form in the cubic Heusler phase as ScPt2In. Despite very different structure types both compounds show very similar, but peculiar magnetic properties. Analysis of susceptibility χ(T), magnetization M(H), specific heat C(T) and resistivity ρ(T) indicate a stable trivalent Yb3+ state, without any sign for a significant Kondo interaction. Nevertheless, C(T) data evidence a very low magnetic ordering temperature, of only 240 mK and 180 mK for YPS and YPI, respectively, connected with a very weak intersite magnetic exchange. This very weak exchange makes these compounds candidates for magnetic cooling. Possible origins for and implications of this weak exchange shall be discussed.
The transition from the ZrPt2Al structure type to the cubic laves phase upon decreasing the size of the R-element has been previously reported for the RPd2Sn and RPd2In series. Our results allow to generalize this observation to a whole series of RT2X compounds and indicate that this transition is mainly induced by a size effect and not related to a particular valence electron count.