  We have studied the extended Hubbard model with pair hopping in the atomic
limit for arbitrary electron density and chemical potential and focus on
paramagnetic effects of the external magnetic field. The Hamiltonian considered
consists of (i) the effective on-site interaction U and (ii) the intersite
charge exchange interactions I, determining the hopping of electron pairs
between nearest-neighbour sites. The phase diagrams and thermodynamic
properties of this model have been determined within the variational approach
(VA), which treats the on-site interaction term exactly and the intersite
interactions within the mean-field approximation. Our investigation of the
general case shows that the system can exhibit not only the homogeneous phases:
superconducting (SS) and nonordered (NO), but also the phase separated states
(PS: SS-NO). Depending on the values of interaction parameters, the PS state
can occur in higher fields than the SS phase (field-induced PS). Some ground
state results beyond the VA are also presented.
