like the external magnetic field or nuclear magnetic moments (average magnetic moment, susceptibility, shielding, and beyond) up to 4th order. We will assume for simplicity that all derivatives of the Hamiltonian beyond first derivatives vanish as is e.g. the case in the LFT Hamiltonian or the Dirac Hamiltonian (i.e., there are no "diamagnetic" terms). We will use the generic notation λ i , λ j , λ k , λ l for the different parameters in the following.