Mössbauer studies on the Fe(II) oxalate spin ladder Na2Fe2(C2O4)3(H2O)2

We investigated the magnetic correlations in the Fe spin ladder system Na2Fe2(C2O4)(3)(H2O)(2) by magnetic susceptibility and Fe-57 Mossbauer spectroscopy between 2 and 310 K. The susceptibility exhibits a broad maximum at about 20 K indicating antiferromagnetic coupling and a S = 0 dimer formation. The Mossbauer measurements reveal a temperature dependent quadrupole splitting and a non-magnetic ground state. The orbital ground state is identified as a singlet with an excited doublet at 383 K in the T-2g manifold.