Impurity effect in a novel spin-Peierls compound TiOBr

We have performed magnetic susceptibility and electron diffraction measurements on impurity effect in a novel spin-Peierls system TiOBr, i.e. Ti1-xScxOBr. The impurity-induced antiferromagnetic long-range order found in Cu1-xZnxGeO3 could not be observed in this system. A number of unpaired spins induced by the impurities can be explained by a simple model that one Sc impurity creates one S=12 spin up to the threshold concentration, xc∼0.025. The induced impurity suppresses the spin-Peierls transition temperature, Tc1 and the spin-Peierls phase disappears at xt∼0.028, although the incommensurate state still persists above xt. Both values agree well with each other.