Elastic Properties and Energy Dissipation Related to the Disorder-Order Ferroelectric Transition in a Multiferroic Metal-Organic Framework [(CH3)2NH2][Fe(HCOO)3] with a Perovskite-Like Structure

The elastic properties and the coupling of ferroelasticity with ferromagnetism and ferroelectricy are crucial for the development of multiferroic metal-organic frameworks (MOFs) with strong magnetoelectric coupling. Elastic properties and energy dissipation related to the disorder-order ferroelectric transition in [(CH3)(2)NH2][Fe(HCOO)(3)] were studied by differential scanning calorimetry (DSC), low temperature X-ray diffraction (XRD) and dynamic mechanical analysis (DMA). DSC result indicated the transition near 164 K. XRD showed the first-order structural transition from rhombohedral R (3) over barc to monoclinic Cc at similar to 145 K, accompanied by the disorder-order transition of proton ordering in the N-H ... O hydrogen bonds in [(CH3)(2)NH2](+) as well as the distortion of the framework. For single crystals, the storage modulus was similar to 1.1 GPa and the loss modulus was similar to 0.02 GPa at 298 K. DMA of single crystals showed quick drop of storage modulus and peaks of loss modulus and loss factor near the ferroelectric transition temperature similar to 164 K. DMA of pellets showed the minimum of the normalized storage modulus and the peaks of loss factor at similar to 164 K with weak frequency dependences. The normalized loss modulus reached the maximum near 145 K, with higher peak temperature at higher frequency. The elastic anomalies and energy dissipation near the ferroelectric transition temperature are caused by the coupling of the movements of dimethylammonium cations and twin walls.

Automated summary

The study investigated the elastic properties and energy dissipation of ferroelectric transition in [(CH3)(2)NH2][Fe(HCOO)(3)] using DSC, XRD, and DMA. The results showed a transition near 164 K, a structural transition, and elastic anomalies and energy dissipation near the ferroelectric transition temperature.