The problem of finite-size effects in $s=1/2$ Ising systems showing slow dynamics of the magnetization is investigated introducing diamagnetic impurities in a ${\mathrm{Co}}^{2+}$-radical chain. The static magnetic properties have been measured and analyzed considering the peculiarities induced by the ferrimagnetic character of the compound. The dynamic susceptibility shows that an Arrhenius law is observed with the same energy barrier for the pure and the doped compounds while the prefactor decreases, as theoretically predicted. Multiple spin reversal has also been investigated.

• Received 4 August 2003

DOI:https://doi.org/10.1103/PhysRevLett.92.207204