Insight into understanding structural relaxation dynamics of [NH2NH3][Mn(HCOO)3] metal-organic formate.

Graphical abstract Highlights • Coexistence of chiral and perovskite phases in [NH 2 NH 3 ][Mn(HCOO) 3 ](HyMn) metal-organic compound. • Dielectric two-power law, generalized Mittag-Leffler response of HyMn. • The presence of polar nanoregions in HyMn suggesting the relaxor nature of the ferroelectricity. Abstract We report the synthesis, thermal and dielectric measurements of [NH 2 NH 3 ][Mn(HCOO) 3 ] (HyMn) compound. Above room temperature this polymeric material undergoes two phase transitions at ∼360 K and ∼298 K, as observed via DSC and BDS spectra. The first high temperature phase transition is associated with the paraelectric to ferroelectric transition of perovskite HyMn. The low temperature phase transition corresponds to the paraelectric to antiferroelectric transition of chiral HyMn. However, mechanisms hidden behind the observed two polymorphic phases are not completely clear yet. Dielectric spectroscopy measurements have revealed formation of clusters and superclusters as well as the relaxor-like behavior of this compound in wide temperature range resulting from both chiral and perovskite phases. Analysis of dielectric permittivity spectra obtained for the investigated material showed the generalized Mittag-Leffler two-power-law relaxation pattern that was interpreted by means the stochastic scenario of correlated-clusters. The proposed approach brought into light the presence of polar nanoregions in the material suggesting the relaxor nature of the existing ferroelectricity. [ABSTRACT FROM AUTHOR]