Exact solution of a decorated ferrimagnetic Ising model

We give the exact solution of a two-dimensional decorated ferrimagnetic Ising model. This model has recently been introduced by Kaneyoshi [Physica A 229 (1996) 166] as a simple ferrimagnetic model which can show more than one compensation temperature. The exact solution is obtained by mapping the model onto the spin- Ising model. We show that two compensation temperatures exist in the model when the decorating spin S is integer. However, only one compensation temperature has been found when S is half-integer.