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College Park, Maryland      June 6 - 10 , 2004

T2-D2 (2:00 PM): Coexistence of superconductivity and magnetism in heavy fermion family of compounds: CeMIn5

A. Llobet (Los Alamos Neutron Science Center, Los Alamos National Laboratory), A.D. Christianson (Los Alamos National Laboratory; Colorado State University), J.S. Gardner (NIST Center for Neutron Research), W. Bao, N.O. Moreno, P.G. Pagliuso, J.L. Sarrao (Los Alamos National Laboratory), J.W. Lynn (NIST Center for Neutron Research; Center for Superconductivity Research, University of Maryland, College Park, MD 20742), J.M. Mignot (Laboratoire Léon Brillouin, C.E.A Saclay, 91191 Gif-sur-Yvette Cedex), K. Prokes (Hahn-Meitner-Institut Berlin)

We report the first evidence of the correlation between long-range magnetic order and the development of a superconducting ground state in the Ce-based heavy fermion family of compounds CeRh1-xMxIn5 (M = Ir, Co). Our neutron diffraction study describes the evolution of the magnetic structure with Ir or Co doping. Upon doping, the ground state is driven from an AFM helical structure (ki=(1/2, 1/2, 0.297)) in CeRhIn5 to a more complex magnetic structure characterized by commensurate and incommensurate components. Remarkably, the presence of the commensurate propagation vector seems strongly correlated with the development of superconductivity in this alloy series. Further, the magnetic structure is unaffected by the development of the superconducting state and a large Ce staggered magnetic moment coexists with superconductivity at low temperatures. Hydrostatic pressures as well as the application of magnetic fields have been also used to destroy or induce the superconducting state, and neutron diffraction studies reveal the interplay between magnetism and superconductivity in this series of heavy fermion compounds. This study lends credibility to the idea that the formation of the unconventional superconducting state may be favored by specific types of magnetic fluctuations. It also provides more evidence of the possible duality of the 4f electrons in these Ce-based compounds.

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