SELF-CONSISTENT CRYSTAL-FIELD DESCRIPTION OF TETRAGONAL PR AND U COMPOUNDS WITH VANVLECK INDUCED MAGNETISM

Many U and Pr compounds presenting localized electron behavior are con veniently described in terms of crystal electric field (CF) acting on the J = 4 ground multiplet. In particular, compounds having the ThCr2S i2- or CaBe2Ge2-type structure are characterized by a tetragonal CF at the magnetic site. We have developed a method allowing us to estimate the five CF parameters in the case of a singlet CF ground state, a si tuation in which a Van Vleck induced magnetism can exist. This is done by imposing a priori some experimental constraints, in particular a s elf-consistent condition on the ordered moment and the ordering temper ature. We apply the method to UPt2Si2, PrFe2Si2, and PrFe2Ge2. In the U compound we find that the value of the ordered moment can be account ed for in the localized model. For the two Pr compounds, we find that details of the CF splittings can produce the two very different values of the ordered moment observed.