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TT: Fachverband Tiefe Temperaturen
TT 43: Correlated Electrons: Heavy Fermions 2
TT 43.1: Vortrag
Donnerstag, 26. März 2009, 15:45–16:00, HSZ 301
Cerium iron oxypnictides: from a heavy fermion system to the parent compound for high-Tc superconductivity — •Anton Jesche, Cornelius Krellner, and Christoph Geibel — Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
Within the layered FeAs systems the CeFePnO (Pn = As, P) compounds offer the unique possibility to study the interplay between strong 3d correlation effects connected with peculiar features of the FeAs layers and strong 4f correlation effects due to interaction between conduction and Ce 4f electrons. Thus we recently showed that CeFePO is a paramagnetic heavy fermion system likely close to a ferromagnetic instability [1] connected with the onset of Ce long range ordering, while Fe is non magnetic. In contrast in CeFeAsO both Fe and Ce orders antiferromagnetically around 140 K and 4 K, respectively, Ce being in a magnetic stable trivalent state due to the larger unit cell volume. In this compound F-doping lead to the suppression of Fe ferromagnetic ordering and to the formation of a superconducting state with a remarkably high Tc of 41 K [2]. We report on measurements of specific heat, electric resistance and magnetization on single crystalline CeFeAsO and CeFePO, as well as on the alloy system CeFeAs1−xPxO. We shall focus on the effect of P for As substitution on the magnetic ordering of Fe and Ce as well as on the superconductivity. Further on we shall address the relation between the Fe magnetic ordering and the structural distortion in pure CeFeAsO around 150 K.
[1] Phys. Rev. Lett. 101, 117206 (2008).
[2] Phys. Rev. Lett. 100, 247002 (2008).