Journal Article

PHPPUBDB-12045

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Structural Phase Transitions in $EuC_2$

Wandner, D. ; Link, P. ; Heyer, O. ; Mydosh, J. ; Ahmida, M. A. ; Abd-Elmeguid, M. M. ; Speldrich, M. ; Lueken, H. ; Ruschewitz, U. ; DESY

2010
American Chemical Society Washington, DC

This record in other databases:        

Please use a persistent id in citations: doi:10.1021/ic901979v

Abstract: Pure EuC(2), free of EuO impurities, was obtained by the reaction of elemental europium with graphite at 1673 K. By means of synchrotron powder diffraction experiments, the structural behavior was investigated in the temperature range from 10 to 1073 K. In contrast to former results, EuC(2) crystallizes in the ThC(2) type structure (C2/c, Z = 4) at room temperature. A tetragonal modification (I4/mmm, Z = 2) is only observed in a very small temperature range just below the transition to a cubic high-temperature modification (Fm3m, Z = 4) at 648 K. DTA/TG investigations confirm these results. According to Raman spectroscopy, EuC(2) contains C(2)(2-) ions (nu(C[triple bond]C) = 1837 cm(-1)). The divalent character of Eu is confirmed by the results of magnetic susceptibility measurements and (151)Eu Mossbauer spectroscopy. In these measurements a transition to a ferromagnetic state with T(C) = 15 K is observed, which is in reasonable agreement with literature data. Above T(C) EuC(2) is a semiconductor according to measurements of the electric resistivity vs temperature, again in contrast to former results. Around T(C) a sharp maximum of the electric resistivity vs temperature curve was observed, which collapses on applying external magnetic fields. The observed CMR effect (colossal magnetoresistance) is much stronger than that reported for other EuC(2) samples in the literature. These investigations explicitly show the influence of sample purity on the physical and even structural properties of EuC(2).

---

Contributing Institute(s):

1. Experiments with synchrotron radiation (HASYLAB)

Research Program(s):

1. DORIS Beamline B2 (POF2-54G13) (POF2-54G13)

Experiment(s):

1. DORIS Beamline B2 (DORIS III)

Appears in the scientific report 2010
Notes: (c) 2009 American Chemical Society. No copyright permission for full text.

---

Database coverage:
; JCR ; No Author Disambiguation ; Thomson Reuters Master Journal List ; Web of Science Core Collection

---