Homometallic ferrimagnetism in the zig-zag chain compound Na2 Cu5 Si4 O14

The structure of Na2 Cu5 Si4 O14 is comprised of zig-zag chains of alternating Cu edge-sharing dimers and trimers, with different magnetic ground states, allowing the occurrence of homometallic ferrimagnetism. The magnetic susceptibility data are consistent with that of a ferrimagnetic chain compound, and are predicted using a model that considers interactions intra-trimers (related to the exchange integral J1 =-224.9 K), intra-dimer (J3 =40.22 K), and inter dimer-trimer (J2 =-8.01 K). The magnetic interaction between the antiferromagnetic trimer and ferromagnetic dimer is in accordance with the Goodenough rules applied to the Cu-O topology. A three-dimensional antiferromagnetic ordering is observed below TN =8 K, corresponding to the magnetic ordering between chains. In addition, since TN ∼ θp there is not a significant degree of frustration in the chain ordering.