Structural, magnetic and dielectric properties of two novel mixed-valence iron(II)-iron(III) metal formate frameworks

摘要

Two novel mixed-valence iron(II)-iron(III) formate frameworks templated by ethylammonium and diethylammonium cations have been prepared and characterized by DSC, X-ray diffraction and spectroscopic methods. We also report dielectric and magnetic properties of the obtained samples. Both MOFs crystallize in the P (3) over bar 1c structure and exhibit magnetic order at 39 K. The analogue with diethylammonium cations undergoes a structural phase transition near 240 K into a triclinic phase. This transition has an order-disorder character and it is associated with pronounced dielectric anomaly. This compound is therefore the second discovered mixed-valence metal formate exhibiting multiferroic properties.