MOMENT REDUCTION BY THE CRYSTAL-FIELD INTERACTION IN ERCU4AL8

A self-consistent mean field calculation of the ordered Er3+ magnetic moment in tetragonal ErCu4Al8 as a function of temperature has been ca rried out assuming that the crystal field wave functions and splitting s of the ground multiplet are known from the fitting of the inelastic neutron-scattering spectra. This calculation accounts well for the str ong reduction of the moment along the c-axis, which has been observed in a recent neutron diffraction experiment for the determination of th e magnetic structure of this compound. The effect of the crystal field on the Er3+ moment is discussed.