Electronic structure calculations were conducted for the CrI3/CrGeTe3 junction with different separations (z) between the two slabs, CrI3 and CrGeTe3, which provide a means to resolve the magneto-volume spin coupling. The calculations demonstrate that high electron mobility, high frequency, and strongly electronic structure modification are obtained at a specific value for slab separation (z). z=0.36238, which is equivalent to the insulating separation of 13.85 Å, is preferable for free-to-move carriers, while the spin wave maximum is at z=18 Å. The moment observed in the DOS of the CrI3 layer supports an increase in the surface field, which in turn explains the effectiveness of the CrI3 layer in tunneling applications. The CrI3 Fermi surface contains small electronic pockets derived from the Cr-3d doubly degenerate state at M. The doubly degenerate effective mass m^* is approximately constant near the bottom of the nearly free electron band, but the triply m^* increases somewhat at the inflection point by the Cr-3d magnetic field. Depending on the number of d-electrons, the junctions CoMnI3/CrGeTe3, MoI3/CrGeTe3 and WI3/CrGeTe3 are examined. The comparison between CoMnI3, MoI3 and WI3, and CrI3 ensures that the performance of the CrI3 layer is due to the activity of Cr-3d, which provides a unique opportunity to control the junction properties. The DOS shape of the MoI3 layer demonstrates fairly interesting magnetic properties that are nearly similar to those of the CrI3 layer.