Crystal field calculation and electron paramagnetic resonance (EPR) ha
ve been performed on zircon-type materials Nd:YMO4 (M=V, As, P). Simul
ation of the energy level schemes has been carried out and the wave fu
nctions composition and g tensor principal values associated to the fi
rst sub-level of the I-4(9/2) manifold were calculated. A rather good
correlation is obtained between crystal field calculations and the EPR
measurements. Furthermore, some extra lines observed by optical spect
roscopy (absorption and emission) also appear on the EPR spectra and a
correlation between the two spectroscopies indicates that Nd3+-Nd3+ e
xchange and dipolar interactions occur in the zircon family, even at v
ery low doping content (less than 8X10(19) Nd3+ ions cm(-3)). Nd3+-Nd3
+ pairs at distances 3.9, 5.9 and 6.3 Angstrom have been identified. (
C) 1998 Elsevier Science S.A.