Multiferroic Behavior Associated with an Order−Disorder Hydrogen Bonding Transition in Metal−Organic Frameworks (MOFs) with the Perovskite ABX₃ Architecture

Abstract

Multiferroic behavior in perovskite-related metal-organic frameworks of general formula [(CH(3))(2)NH(2)]M(HCOO)(3), where M = Mn, Fe, Co, and Ni, is reported. All four compounds exhibit paraelectric-antiferroelectric phase transition behavior in the temperature range 160-185 K (Mn: 185 K, Fe: 160 K; Co: 165 K; Ni: 180 K); this is associated with an order-disorder transition involving the hydrogen bonded dimethylammonium cations. On further cooling, the compounds become canted weak ferromagnets below 40 K. This research opens up a new class of multiferroics in which the electrical ordering is achieved by means of hydrogen bonding.

Magnetic field-temperature phase diagram of multiferroic [(CH3)2NH2]Mn(HCOO)3<

“…We extract J=-0.69 K. 34 This value compares well with that estimated from the zero field susceptibility (-0.64 K), 13 although the absence of adjustable fit parameters makes it much less ambiguous. 35 The overall low energy scale of the exchange interactions explains why the spins can be saturated in experimentally-realizable fields.…”

“…13,27 Magnetization measurements were performed using a 65 T short-pulse magnet at the National High Magnetic Field Laboratory in Los Alamos using a 1.5 mm bore, 1.5 mm long, 1500-turn compensated-coil susceptometer, constructed from 50 gauge high-purity copper wire. The sample was loaded into a 1.3 mm diameter ampoule that moves in and out of the coil.…”

“…13,14 Cross-coupling between the electric and magnetic orders has been observed, [15][16][17][18] and low temperature phase separation leads to quantum tunneling of the magnetization. 19 Figure 1 displays the crystal structure of this compound and summarizes the aforementioned energy scales.…”

Low-frequency Raman study of the ferroelectric phase transition in a layeredCuCl4-based organic-inorganic hybrid

“…42,43 However, the structural phase transitions observed in the layered-type hybrids, although widely investigated, had never been connected to polar ordering until recently when the possibility of combined ferromagnetic and ferroelectric order and, consequently, multiferroicity was considered. [44][45][46] A prime example of a perovskite-based layered hybrid undergoing both ferromagnetic (T = 13 K) and ferroelectric (T = 340 K) ordering is (C 6 H 5 CH 2 CH 2 NH 3 ) 2 CuCl 4 (Ref. 40) (PEACuCl), the subject of this paper.…”

Multiferroic Materials: Physics and Properties

“…Temperature dependent X-ray diffraction analysis showed that an order-disorder-type phase transition from a high temperature rhombohedral paraelectric phase to a low temperature monoclinic ferroelectric phase coincided with the dielectric anomaly, rendering the material as a potential multiferroic. 50 Recent theoretical calculations predict a ferroelectric polarization of B2 mC cm À2 for this compound, which can be increased up to B6 mC cm À2 by choosing different organic A cations. 49 …”