Phase transition of transverse Ising model in a random field

The phase diagrams of a transverse Ising model with a random field are studied within the framework of an effective-field theory with correlations. We find that the reentrant phenomenon of second order is possible for the system with a coordination number z larger than z=4, when the applied random field is bimodal. The reentrant phenomenon comes from the competition between the transverse field and the random field, especially near the critical region where the tricritical behavior disappears.