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

Abstract

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)2NH2][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 R3−c to monoclinic Cc at ~145 K, accompanied by the disorder-order transition of proton ordering in the N–H…O hydrogen bonds in [(CH3)2NH2]+ as well as the distortion of the framework. For single crystals, the storage modulus was ~1.1 GPa and the loss modulus was ~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 ~164 K. DMA of pellets showed the minimum of the normalized storage modulus and the peaks of loss factor at ~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.

Elastic Properties and Energy Loss Related to the Disorder–Order Ferroelectric Transitions in Multiferroic Metal–Organic Frameworks [NH4][Mg(HCOO)3] and [(CH3)2NH2][Mg(HCOO)3]

“…The peak temperature tends to be independent of frequency, and the peak height tends to decrease with the increase in frequency, indicating the features of the first-order phase transition. The elastic anomalies and energy loss related to the ferroelectric transition in [(CH 3 ) 2 NH 2 ][Mg(HCOO) 3 ] were similar to those reported for [(CH 3 ) 2 NH 2 ][Mn(HCOO) 3 ] and [(CH 3 ) 2 NH 2 ][Fe(HCOO) 3 ] investigated by DMA [ 39 , 53 ].…”

“…DMA measurements of the single crystals of [NH 4 ][Mg(HCOO) 3 ] and [(CH 3 ) 2 NH 2 ][Mg(HCOO) 3 ] were carried out using DMA8000 instruments (PerkinElmer Instruments, Waltham, MA, USA) in the single cantilever mode from 160 K to 320 K at the rate of 2 K/min. DMA measurements of pellets of [NH 4 ][Mg(HCOO) 3 ] and [(CH 3 ) 2 NH 2 ][Mg(HCOO) 3 ] were carried out in the compression mode using PerkinElmer Instruments Diamond DMA (PerkinElmer Instruments, Waltham, MA, USA) in the range of 140–300 K at 2 K/min during heating processes, as described in [ 39 , 53 ].…”

“…The ferroelectric transition temperature is the highest when M is Mg, because Mg 2+ is the hardest Lewis acid among them, leading to the strongest hydrogen bonds [ 35 ]. Furthermore, the spin-canted antiferromagnetic ordering transitions in [(CH 3 ) 2 NH 2 ][M(HCOO) 3 ] (M = Mn, Co, Ni, Fe, Cu) occur below 40 K (Ni: 35.6 K, Fe: 20 K, Co: 14.9 K, Mn: 8.5 K, Cu: 5.2 K) due to the metal ions within the framework skeletons, and the spin reorientation transitions in [(CH 3 ) 2 NH 2 ][M(HCOO) 3 ] (M = Co, Ni) occur at 13.1–14.3 K (Co: 13.1 K, Ni: 14.3 K) [ 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ]. The effect of pressure on the structure and the electric and magnetic properties of [(CH 3 ) 2 NH 2 ][M(HCOO) 3 ] (M = Mg, Mn, Co, Zn, Cd) was investigated [ 37 , 47 , 54 , 55 , 56 ].…”