SPIN-DENSITY AND MAGNETISM OF RARE-EARTH NICKEL BOROCARBIDES - RNI(2)B(2)C

The rare-earth spin moments in quarternary borocarbides RNi(2)B(2)C, R =Pr, Nd, Sm, Gd, Ho, Tm are determined by self-consistent density func tional theory, using the embedded cluster formalism. Spin-polarized el ectronic structure calculations considering antiferromagnetic coupling between R-C layers are performed. Spin polarization of the lattice is examined in detail and related to observed ferromagnetic ordering in R-C layers and antiferromagnetic ordering between layers. The observed superconductivity of Y, Lu, Tm, Er, and Ho compounds and regions of c oexistence with antiferromagnetism in Tm and Ho is discussed in terms of the magnitude of R moments, differences in R 4f-5d hybridization, a nd resulting lattice polarization.