MAGNETIC OPERATORS FOR TI3-STATES( AND CU2+ GROUND)

We have checked the XMCD sum rules through an analytical calculation o f Cu2+ L-2,L-3 edges in octahedral symmetry. It is found that XMCD sum rules are fully satisfied in the framework of the crystal field multi plet approach resulting from the very general arguments developed in t heir derivations by B.T. Thole and collaborators. Analytical expressio ns for the orbital magnetic moment [L-z] the spin magnetic moment [S-z ] and the magnetic dipole term [T-z] are obtained as functions of crys tal field strength and spin-orbit couplings. The nullity of [T-z] is s pecially examined through group theory considerations, and it is found that at low temperature the [T-z] contribution can be much larger tha n the [S-z] contribution in the spin sum rule. The case of Ti3+ in oct ahedral symmetry is also considered and it is found that, even for no spin-orbit coupling, [T-z] can be non-zero. (C) 1997 Elsevier Science B.V.