Abstract
We investigated the effect of doping on the crystallographic, dynamic
and magnetic properties of(Cu1-zZnz)GeO3 as well as Cu(Ge(1-x)A(x))O-3
with A=Al, Si, Ga, As, In, Sn, Sb and Ti. A large solubility was only
observed for Zn, Si and Ti. For those elements, the lattice parameters
show a linear dependence on doping within the whole solubility range.
The spin-Peierls transition temperature T-SP decreases linearly with
doping, though the slope is strongly dependent on the dopant. For
Zn-doping, a Neel-like ground state which exhibits spin-flop behavior
appears for higher doping after the complete disappearance of the
spin-Peierls ground state. Si- and Ti-doped samples exhibit a similar
phase in a coexistence with the spin-Peierls ground state. The analysis
of the susceptibility in the spin-Peierls phase for low Zn content
indicates a reduction of the dimerization within the Cu chains and the
energy gap upon doping. Whereas for Si and Ti all phonon frequencies
changed linearly with the doping level, we observed in Zn-doped samples
for some phonons a clear minimum at the composition z=0.02 where the
spin-Peierls transition disappears, suggesting a strong spin-phonon
coupling for these modes. For higher Zn concentrations, no lattice
dimerization can be observed by Raman scattering.
