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MA: Fachverband Magnetismus
MA 32: Postersession II: Spinstruct./Phase Trans. (1-10); Spinelectronics (11-15); Thin Films (16 - 36); Particles/Clusters (37-45); Multiferroics (46-54); Spindynamics/Spin Torque (55 - 76); Post Deadlines (77-79)
MA 32.8: Poster
Friday, February 29, 2008, 11:15–14:00, Poster E
Study of EuCu2(Ge1−xSix)2 across a quantum critical point — •Mahmoud A. Ahmida1, Dirk Johrendt2, Zakir Hossain3, Christoph Geibel4, and Mohsen M. Abd-Elmeguid1 — 1II Physikalisches Institut, Universität zu Köln, Köln, Germany — 2Department Chemie and Biochemie der Ludwig-Maximilians-Universität München, München, Germany — 3Department of Physics, Indian Institute of Technology, Kanpur, India — 4Max Planck Institut für Chemische Physik fester Stoffe, Dresden, Germany
The intermetallic series EuCu2(Ge1−xSix)2 crystallizing in the tetragonal ThCr2Si2-type structure combines the antiferromagnetic (AF) compound EuCu2Ge2 (TN=14 K) with the homogenous intermediate valent (IV) compound EuCu2Si2. Therefore, the system offers the opportunity to investigate the crossover from a magnetically ordered state to a nonmagnetic IV state through a quantum critical point (QCP) at x ≈ 0.65. To gain a microscopic insight into the change of the magnetic and valence states and their competition at the QCP, we have performed systematic 151Eu Mössbauer effect measurements on EuCu2(Ge1−xSix)2 as a function of concentration (0 ≤ x ≤ 1) at different temperatures (300 to 4 K). The analysis of the results shows that the collapse of AF ordering for x > 0.50 is associated with a simultaneous sharp increase of the valence state of Eu towards the Eu+3state. It is shown that the simultaneous valence /magnetic phase transition across the QCP is of first-order.