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.

Graphical abstractThe 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 full-size imageDownload 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.