The effect of dipolar interaction on the magnetic isotope effect

► A multi-channel kinetic description of the magnetic isotope effect is formulated. ► The hyperfine interaction gives two channels in zero field, while the electron spin dipole-dipole interaction gives four channels thus potentially doubling the effect. ► The dipole induced effect may be large even for a strong exchange interaction. ► The dipolar interaction is responsible for the huge effect observed experimentally in ATP synthesis with magnetic Mg.