Absorption and Zeeman effect in Nd3+-doped LiYF4: Measurements and simulation

The Nd3+ ion energy level scheme in a LiYF4 crystal host is re-examined by absorption spectroscopy and Zeeman measurements. Some other Kramers doublets have been observed. A total of 137 experimental levels has been input in the fitting procedures before the application of the magnetic field. The calculations were performed assuming the approximate D-2d rare-earth site symmetry, and the correct S-4, With all parameters varying freely. In both symmetries we have obtained a rms deviation of 17.7 cm(-1). In the presence of a magnetic field B, linear and non-linear anticrossing degeneracy lifting, together with negligible Kramers degeneracy lifting, has been observed. In particular, with B perpendicular to c, the third component of the (4)G(7/2) level behaves in the former way with a splitting of 22 cm(-1), for B = 6.3 T, and (4)G(5/2) behaves in the latter way (B parallel to c). It was possible only to describe these features all together by introducing the magnetic Hamiltonian mu B(L + g(e)S) in the secular determinant before diagonalization. Then, the 364 eigenstates and eigenfunctions of the 4f(3) configuration are calculated. The isolated doublets in the energy level scheme and having a small value of the g-factor, split linearly. In this situation, the framework of perturbation theory was used to obtain satisfactory splitting s-factors. Those not isolated or with a large g-factor have a non-linear anticrossing behaviour. The splitting of the lowest component of the I-4(9/2) ground-state multiplet is observed through a transition which is present in the lowest Zeeman component of the F-4(7/2) level. This is quite well reproduced by the simulation.