Magnetic resonance probing of ferroelectricity and magnetism in metal-organic frameworks.

We employ electron paramagnetic resonance (EPR) of the spin probe Mn²⁺ to study the paraelectric − ferroelectric transition in Dimethylammonium Manganese Formate (DMMnF) and Mn²⁺-doped Dimethylammonium Zinc Formate (DMZnF), which are considered model metal − organic frameworks (MOF) with a Pb-free perovskite architecture. In DMMnF, we study the variation of the Mn²⁺ EPR line shape and intensity at the X-band (∼9.4 GHz) and over 80 to 300 K, and we show the absence of magnetoelectric coupling at the ferroelectric transition. At the antiferromagnetic transition in DMMnF, we detect a magnetoelectric coupling caused by weak ferromagnetism in the AFM phase. In DMZnF, EPR spectra of the Mn²⁺ probe combined with DFT show that the crystal field is predominantly determined by the Dimethylammonium (DMA⁺) cations. [ABSTRACT FROM AUTHOR]