AbstractThe value of 9.27 × 10−23J for the exchange coupling parameter between the Ho and Co spins in Ho2Co17has been derived. Some experimental evidence is given to show that the R–T spin coupling parameter is rather insensitive to the kind of the rare earth atom as well as on the cobalt composition. It allows to calculate the intersublattice molecular fields for the rare earth–cobalt intermetalic compounds. This field affects the R magnetic moment and originates from the Co sublattice in the R2Co17, RCo5, R2Co7, RCo3, and RCo2compounds. The fields in the new magnetic materials of the R2Co14B type have also been eva