Synthesis and structure of a new family of 3d–4f heterometallic compounds Rb7LnFe6O2(PO4)8 (Ln=Sm, Eu, Gd, Dy): Magnetic properties of the Sm-, Gd-, Dy-derivatives

A new family of mixed lanthanide(III) and iron(III) oxo-phosphate phases, Rb7LnFe6O2(PO4)8 (Ln=Sm 1, Eu 2, Gd 3, Dy 4), was isolated by using a high-temperature, solid-state method in molten-salt media. The X-ray single-crystal structure analysis shows that these isomorphic derivatives crystallize in a triclinic space group P–1 (no. 2); Z=1. The 3-D framework of these 3d–4f oxo-phosphates are comprised of LnO6 octahedral, FeO5 trigonal bipyramidal (tbp), and μ3-oxo [Fe4O18] tetrameric units interconnected through PO4 tetrahedra. The preliminary results of the temperature-dependent magnetic susceptibility measurements for selected compounds (1, 3, 4) reveal antiferromagnetic-like behavior. 1 shows a weak antiferromagnetric ordering at TN=∼7 K while others show little evidence of long-range magnetic order down to 2 K. All three compounds have measured magnetic moments significantly smaller than the expected values.

The extended framework is described by the connectivity of three distinct types of paramagnetic units. The temperature-dependent, lower than expected effective magnetic moments are reported.Figure optionsDownload as PowerPoint slideHighlights
► A new family of mixed lanthanide(III) and iron(III) oxo-phosphates is isolated.
► Features PO4-linked paramagnetic units of LnO6, FeO5, and μ3-oxo [Fe4O18].
► Sm-derivative orders at TN∼7 K while Gd- and Dy-derivatives show absence of order.