Crystal-Fields at Rare-Earth Sites in R sub 2 Fe sub 14 B Compounds

摘要

Crystal-field effects are expected to be important in R sub 2 Fe sub 14 B compounds. Within a model-independent approach, it is proved that four distinct rare-earth sites exist with respect to the crystalline electric fields, namely, R(4f; z=0), R(4f; z=0.5 c), R(4g; z=0), and R(4g; z=0.5 c), and relationships are established between the corresponding crystal-fields coefficients. Further, generalized Stevens parametrizations of the crystal field coefficients are derived at three levels of approximation for the interatomic forces inside the crystal. A crystal lattice dressing effect upon the radial electronic integrals is found to occur, the magnitude of which depends on the deviation of the interatomic forces from Coulombian. Finally, computation of crystal-field coefficients in Nd sub 2 Fe sub 14 B leads to results which raise questions about the validity of the simple Coulomb point-charge model. 29 refs, 1 tab. (Atomindex citation 17:063528)