# Dresden 2006 – wissenschaftliches Programm

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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 CuCl**_{2} — •Michael Banks^{1}, Reinhard K Kremer^{1}, and Bachir Ouladdiaf^{2} — ^{1}MPI-FKF, 70569 Stuttgart — ^{2}ILL Grenoble, CEDEX 9

Historically, the binary CuCl_{2} and the structurally similar
CuBr_{2} 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 CuBr_{2}). 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 CuCl_{2}) indicating appreciable
inter-chain coupling. To the best of our knowledge, the magnetic
structures of CuCl_{2} and CuBr_{2} remain unsolved until now.
We studied the afm ordering of CuCl_{2} and CuBr_{2} in detail
by neutron powder diffraction using ILL’s high flux powder
diffractometer D20 in its high resolution option. Using single
crystals of CuCl_{2}, we used the 4-circle diffractometer D10
also at the ILL to conclusively solve the magnetic structure. The
magnetic structure of CuCl_{2} 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} ≈
4*T*.