We report a comprehensive study of the x-ray magnetic circular dichroism (X
MCD) at the Ni L-2,L-3 edges of NiFe2O4 (trevorite), a ferrimagnetic compou
nd which belongs to the class of strongly correlated 3d systems. The measur
ed XMCD line shape is in good agreement with full-multiplet calculations fo
r a 3d(8) ground state including an octahedral crystal field of 10Dq = 1.2
eV. Using the XMCD sum rules, we find for the nickel an orbital to spin mag
netic moment ratio of L/S = 0.27 +/- 0.07, which means that the orbital con
tribution to the magnetic moment is 12 +/- 2 %. The size of the error bar i
s not due to the neglect of band structure and hybridization, but due to Co
ster-Kronig transitions which give a transfer of spectral weight in the dic
hroism near the L-2 edge. Using the sum rules for the isotropic x-ray absor
ption spectrum, we obtain the expectation value of the spin-orbit interacti
on, which can be converted into an L/S ratio of 0.34 +/- 0.11. All sum-rule
results were corrected for the influence of core-valence exchange interact
ion, which gives rise to jj mixing between the two absorption edges. The co
rrection is done by comparing the calculated sum-rule results with the corr
ect ground-state values calculated as a function of crystal-field strength.
The 2-eV shoulder of the L-3 line shows a strong positive dichroism, which
can be attributed to a spin-flip state. From the overall agreement between
the experimental and theoretical results, we conclude that a localized mod
el provides a good description for the orbital magnetization. [S0163-1829(9
9)12005-8].