  We present and analyze a minimal exactly solved model that exhibits a
mixed-order phase transition known in the literature as the Thouless effect.
Such hybrid transitions do not fit into the modest classification of
thermodynamic transitions and as such, they used to be overlooked or
incorrectly identified in the past. The recent series of observations of such
transitions in many diverse systems suggest that a new taxonomy of phase
transitions is needed. The spin model we present due to its simplicity and
possible experimental designs could bring us to this goal. We find the
Hamiltonian of the model from which partition function is easily calculated.
Thermodynamic properties of the model, i.e. discontinuous magnetization and
diverging susceptibility, are discussed. Finally, its generalizations and
further research directions are proposed.
