ANTIFERROMAGNETIC ORDER IN THE THCR2SI2 TYPE PHOSPHIDES CACO2P2 AND CECO2P2

Magnetic susceptibility and neutron powder diffraction experiments rev eal that the cobalt atoms in CaCo2P2 and CeCo2P2 order antiferromagnet ically below the Neel temperatures T-N=113(2) K and T-N=440(5) K, resp ectively. In these tetragonal compounds with ThCr2Si2 type structure ( I4/mmm) the magnetic moments of the cobalt atoms are ordered ferromagn etically within the basal plane and antiferromagnetically along the c axis with the stacking sequence +-, +-, corresponding to a propagation vector k=(0, 0, 1). In the calcium compound the cobalt moments with m u(exp)=0.32(2) mu(B) are ordered perpendicular to the c axis, whereas in the cerium compound these moments with mu(exp)=0.94(2) mu(B) are al igned parallel to this axis. The magnetic properties of the previously investigated cobalt containing phosphides ACo(2)P(2) (A = Sr, La, Pr, Nd, Sm, Eu) are briefly reviewed. The magnetic ordering temperatures and the magnetic moments of the cobalt atoms correlate with the formal charge of the cobalt-phosphorus polyanion and with the Go-Co distance s. (C) 1998 Elsevier Science S.A.