MAGNETIC AND ELECTRICAL-PROPERTIES OF A NEW SERIES OF RARE-EARTH SILICIDE CARBIDES WITH THE COMPOSITION R3SI2C2 (R = Y, LA-ND, SM, GD-TM)

The 12 title compounds have been prepared by arc-melting cold-pressed pellets of the elemental components and subsequent annealing, They cry stallize with an orthorhombic structure and with cell dimensions varyi ng between a = 403.9(1) pm, b = 1688.4(2) pm, and c = 450.6(1) pm for La3Si2C2 and a = 379.6(1) pm, b = 1532.8(2) pm, and c = 414.5(1) pm fo r Tm3Si2C2, The magnetic properties of these compounds were determined with a SQUID magnetometer between 2 and 300 K with magnetic flux dens ities up to 5.5 T. Y3Si2C2 is a Pauli paramagnet. The cerium atoms in Ce3Si2C2 are trivalent; at low temperatures this compound is ferro- or ferrimagnetic with an ordering temperature of 10(+/-3) K. Pr3Si2C2 an d Nd3Si2C2 are ferromagnetic (T-C = 25(+/-3) and 30(+/-3) K, respectiv ely), whereas the silicide carbides R3Si2C2 with R = Sm and Gd-Tm are antiferromagnetic. Ho3Si2C2, Er3Si2C2, and Tm3Si2C2 show metamagnetic transitions. The highest ordering temperature occurs for Gd3Si2C2 with a Neel temperature T-N = 50(+/-1) K, The electrical conductivities of several compounds were determined between 5 and 300 K, They indicate metallic behavior, and in several cases they reflect the magnetic orde ring temperatures. (C) 1998 Academic Press.