Magnetic properties of a new 3D-cobalt phosphonate: Co3(O3PC2H4CO2)2

The magnetic properties of a new cobalt(II) phosphonate have been investigated. The compound is isostructural with the pillared layered metal phosphonates M 3 (O 3 PC 2 H 4 CO 2 ) 2 , M=Zn, Mn. In this structure, the magnetic transition metal ions are arranged within layers formed by the interconnection of CoO 4 tetrahedra and CoO 6 octahedra. The ac and dc magnetic susceptibilities and magnetization measurements show that Co 3 (O 3 PC 2 H 4 CO 2 ) 2 is a canted antiferromagnet at T N =15.5 K. Below T N , the hysteresis cycles exhibit an S shape related to a spin flop effect. The specific heat measurements indicate that large short-range correlations are present above T N in relation with the layered character of the structure.