Untersuchung von magnetischen Anregungen in Kupraten mit Seltenen Erden Abschlussbericht

Recently the magnetic and caloric data of Nd_1_._8Ce_0_._2CuO_4 have been under controverse discussion. One way of interpretation characterizes this material as a new heavy fermion with a new mechanism. On the other hand it has been proposed that a softening of low energy spin wave exitations of Nd is responsible for the high density of states found at low temperatures. In this case the ground state would be a spin glass. We have performed muon spin rotation (#mu#SR) and NMR studies on (NdCe)_2CuO_4 and related substances. The main result is, that the Nd spin fluctuations in Nd_1_._8Ce_0_._2CuO_4 slow down below 2 K. Below 0.7 K this dynamics remains constant with fluctuation rates of about 10"9 s"-"1. Neither a magnetically ordered nor a frozen spin glass state can be reached down to 70 mK. This fact supports the model of a new heavy fermion. We found similarly slow spin dynamics in hole-doped (La, RE)SrCuO_4 compounds. Its origin is supposed to be a dynamic stripe structure of domains. Whether similar structures occur also in the electorn-doped materials has to be investigated. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(67,15) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman