  We present the influence of spin correlation on the metal-insulator
transitions (MIT) in two-orbital Hubbard models by the Kotliar-Ruckenstein
slave-boson approach. In the asymmetric half-filling situation, the two orbits
simultaneously transit from conducting to insulating states with the increase
of Coulomb correlation, accompanied by a paramagnetic (PM)-antiferromagnetic
(AFM) transition. The orbital selective Mott transition found in the PM
condition is completely suppressed over a wide correlation range, though it may
exist in the systems away from half-filling. In the insulating state, the
system crosses over from a partially-polarized spin-gapped phase in the
intermediate correlation regime to an almost fully-polarized Mott insulating
phase in the strong correlation regime. These results demonstrate that the spin
modulation to the quasiparticle spectra brings much rich and more interesting
MIT scenario in multi-orbital correlated systems.
