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 functional theory, using the embedded cluster formalism. Spin-polarized electronic 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 coexistence with antiferromagnetism in Tm and Ho is discussed in terms of the magnitude of R moments, differences in R 4f-5d hybridization, and resulting lattice polarization.