  The temperature dependence of the static magnetic susceptibility of
exchange-disordered antiferromagnetic Heisenberg spin-1/2 finite chains with an
odd number of spins is investigated as a function of size and type of disorder
in the exchange coupling. Two models for the exchange disorder distribution are
considered. At sufficiently low temperatures each chain behaves like an
isolated spin-1/2 particle. As the size of the chains increases, this analogy
is lost and the chains evolve into the thermodynamic limit behavior. The
present study provides a simple criterion, based on susceptibility
measurements, to establish when odd-sized chains effectively simulate a single
spin-1/2 particle.
