Abstract: The thickness dependence of the Curie temperature for the ultra-thin ferromagnetic films ranging in thickness from 4 to 7 monolayers has been calculated by considering the effects of the bound condition on the state and configuration of the electron and consequently on the exchange couplings between spins. The results show that the Curie temperature decreases with the reduction of the film's thickness. This confirms the general theoretical expectation from the microscopic point of view and explains the recent experimental results.

Key words: Curie temperature, ultrathin ferromagnetic film, dimensional crossover