where m = L + g e S is the magnetic moment, with L = ∑ N e i l iDy the total electronic angular momentum with respect to the position of the Dy(III) atom, S = ∑ N e i s i the total spin angular momentum, and g e the magnetic g factor of the electron. The electronic wavefunctions Ψ 0 and Ψ 1 are a Kramers pair for the system at zero magnetic field. The three eigenvectors of G are the directions of the three principal magnetic axes.