X*

Defects in spin chains were a subject of great interest over the last decades.The spin-Peierls systems like the organic spin chains compounds (o-DMTTF)₂X (X = Cl,Br,I) have an S = 0 ground state. However it is known [1] that a break in the translational symmetry induces S = 1/2 ground state made by hundreds of spins of the chain. A low temperature paramagnetic signal is often observed and commonly attributed to extrinsic impurities.
By means of Electron Paramagnetic Resonance on (o-DMTTF)₂X ,we show that the paramagnetic signal is intrinsic to the chain. Despite an important concentration of spins, we observed a long relaxation and coherence times and we performed Rabi oscillations on this two levels N body system [2].These characteristics are compatible with quantum information processing. We present the role of isotropic Heisenberg exchange interaction in the reduction of relaxation effect du to the spin bath.