Coexistence of magnetic ordering and ferroelectricity in a Dy-nitronyl nitroxide chain

Abstract

A new nitronyl nitroxide radical-Dy chain having the formula [Dy(hfac)₃(NITPh2OEt)]_n (1) has been obtained by the reaction of nitronyl nitroxide radical NITPh2OEt (NITPh2OEt stands for 2-(2′-ethoxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) with Dy(hfac)₃·2H₂O (hfac represents hexafluoroacetylacetonate). This Dy-rad chain crystallizes in a polar point group of C₂ and has a one-dimensional structure in which the Dy atoms are linked by the NIT-Ph2OEt radical via its two NO groups. The observed P–E hysteresis loops demonstrate its ferroelectric behavior. Magnetic investigations further confirm that in this magnetic system ordering occurs at ca. 3.9 K. Moreover, when the interchain interactions of complex 1 are counteracted by applying a dc field, the frequency-dependent ac signals are observed for 1, implying slow magnetic relaxation. Remarkably, this radical–metal chain represents an unprecedented example of the coexistence of magnetic ordering and ferroelectricity for Ln–nitronyl nitroxide radical compounds.