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J. Larrea Jiménez, S. Paschen, H. Ronnow, J. Teyssier, L. Keller, H. Luetkens:
"QUANTUM CRITICALITY IN THE HEAVY FERMION COMPOUND CeCoGe3-xSix";
Vortrag: 9th Prague Colloquium on f-electron systems, Prag (eingeladen); 31.05.2010 - 03.06.2010.

Quantum Criticality in the heavy fermion compound CeCoGe3􀀀xSix
Julio Larrea J.1, S. B. Paschen1, H. M. Ronnow2, J. Teyssier3, L. Keller4, H. Luetkens4
1Institute of Solid State Physics, Vienna University of Technology, Austria
2Laboratory for Quantum Magnetism, Ecole Polytechnique Fdrale de Lausanne, Switzerland
3Dep. Phys. Cond. Matt., University of Geneve, Switzerland
4Paul Scherrer Institut, Switzerland
We repot a study of the magnetic quantum critical point (QCP) induced by pressure (P) in heavy fermion
(HF) CeCoGe3􀀀xSix compound. Our electrical resistivity measurements under P show general characteristics
of Doniach diagram for HF, with a QCP around PC=6.2(2) kbar. Encouraged by these results, we have
performed muon spin rotation (muSR) and neutron powder diffraction spectroscopy at x=0 and 0.9. Our preliminary
data analysis revealed for both concentrations more than one non-equivalent muon site which could be
ascribed to two different types of environment of magnetic Ce ions. In addition, the T-dependence of frequency
of the muon rotation, which is proportional to the internal magnetic field at the muon site, shows a magnetic
ordering transition (Tm) for CeCoGe2:1Si0:9 at 3.7K while for CeCoGe3 there are three different Tm = 20.3,
11.4 and 7.5 K. So far, evidences of these three magnetic transitions have been only reported by macroscopic
measurements on the pure x=0 single crystalline compound. All of our findings indicate that the coexistence
(or competition) between two dimensional antiferromagnetic spin fluctuations and Griffiths phase disorder is a
possible mechanism to account for the quantum criticality in CeCoGe3􀀀xSix.
Email of the presenting author: larrea@ifp.tuwien.ac.at