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MA: Magnetismus

MA 12: Kondo / Heavy Fermions

MA 12.1: Vortrag

Montag, 27. März 2006, 16:30–16:45, HSZ 403

Magnetic ground state of the frustrated one dimensional binary compound CuCl₂ — •Michael Banks¹, Reinhard K Kremer¹, and Bachir Ouladdiaf² — ¹MPI-FKF, 70569 Stuttgart — ²ILL Grenoble, CEDEX 9

Historically, the binary CuCl₂ and the structurally similar CuBr₂ are among the very first systems the magnetic properties of which were analyzed in terms of a linear spin chain arrangements. Low-dimensional magnetism with typical signatures, e.g. a broad short-range ordering maxima in the susceptibility and heat capacity, have been found. The antiferromagnetic (afm) intra-chain exchange parameters are significant (e.g. ≈320K for CuBr₂). However, both systems are far from representing ideal one-dimensional magnets as must be concluded from the rather high transition temperatures to long-range ordering (e.g. 24 K for CuCl₂) indicating appreciable inter-chain coupling. To the best of our knowledge, the magnetic structures of CuCl₂ and CuBr₂ remain unsolved until now. We studied the afm ordering of CuCl₂ and CuBr₂ in detail by neutron powder diffraction using ILL’s high flux powder diffractometer D20 in its high resolution option. Using single crystals of CuCl₂, we used the 4-circle diffractometer D10 also at the ILL to conclusively solve the magnetic structure. The magnetic structure of CuCl₂ will be presented as showing helicoidal ordering along the chain direction with an incommensurate propagation vector τ = [0.5,0.224,0]. The magnetic phase diagram will be presented showing a spin-flop phase along the chain direction at H_SF ≈ 4T.