Electrical and magnetic properties of layered oxypnictide LaOCoPn (Pn P, As)

Abstract

We have succeeded to prepare LaOCoPn (Pn P, As) by sintering La, CoO and Pn at 1223 K for 48 h in a vacuum. LaOCoPn is isostructural to the new superconductor LaOFeP. The lattice constants a and c of LaOCoP and LaOCoAs are 0.398 and 0.837 nm, and 0.405 and 0.848 nm, respectively. The LaOCoP and LaOCoAs show a metallic behavior below 300 K, and do not show superconductivity above 3 K. Both compounds are ferromagnets. The Curie temperature of LaOCoP is 34 K and that of LaOCoAs is 59 K. The saturated magnetic moments of LaOCoP and LaOCoAs at 5 K are 1.4 x 103 and 2.6 x 103 emu/mol, respectively. The value for LaOCoAs indicates 0.5μB/Co and agrees with the theoretical value recently reported. The absence of the superconductivity in LaOCoPn is considered to be due to the ferromagnetic interaction of Co ions. © 2009 IOP Publishing Ltd.