6424-20-0Relevant articles and documents
Mechanosynthesis of multiferroic hybrid organic-inorganic [NH4][M(HCOO)3] M = Co2+,Mn2+,Zn2+,Ni2+, Cu2+ formate-based frameworks
Bersani, Danilo,Calestani, Davide,Cugini, Francesco,Gemmi, Mauro,Griesi, Andrea,Orlandi, Fabio,Righi, Lara,Solzi, Massimo,Vit, Valentina
supporting information, (2021/12/23)
The family of compounds with formula [NH4][M(HCOO)3], with M a divalent D-metal, is characterized by porous frameworks hosting NH4+ cations exhibiting at low temperature a spontaneous ferroelectric polarization. The presence of magnetically active divalent metal determines the occurrence of antiferromagnetic ordering below 30 K opening the avenue for a rational formulation of a new class of multiferroic materials. We demonstrate that this intriguing class of compounds can be synthetized with a mechanochemical approach. This novel route of synthesis was applied to the series [NH4][M(HCOO)3] with M= Cu2+, Co2+, Mn2+, Zn2+ and Ni2+ using as reactants ammonium formate and the corresponding di-hydrated metal formates. The milling duration of the process correlates with the thermal stability of the di-hydrated metal formates indicating that the first step of the mechanosynthesis process is represented by the removal of water molecules. The characterizations of the final products indicate the presence of single phase [NH4][M(HCOO)3] compounds with an excellent degree of crystallinity.
Magnetic behavior of the metal organic framework [(CH3)2NH2]Co(HCOO)3
Vinod,Deepak,Sharma, Shilpam,Sornadurai,Satya,Ravindran,Sundar,Bharathi
, p. 37818 - 37822 (2015/05/13)
In this study we examine the phase transitions in single crystals of [(CH3)2NH2]Co(HCOO)3, using magnetization and specific heat measurements as a function of temperature and magnetic field. Magnetisation measurements indicate a transition at 15 K that is associated with an antiferromagnetic ordering. Isothermal magnetization versus magnetic field curves demonstrate the presence of a single-ion magnet phase, coexisting with antiferromagnetism. A peak in specific heat is seen at 15 K, corresponding to a magnetic transition and the enthalpy of the transition evaluated from the area under the specific heat peak which decreases with the application of a magnetic field of up to 8 T. This is suggestive of long range antiferromagnetic magnetic order, giving way to single-ion magnetic behavior under an external magnetic field. At high temperatures, the specific heat measurements show a peak at ~155 K that is insensitive to the applied magnetic field. Raman scattering studies confirm the presence of a structural transition. The magnetisation in this temperature range, while exhibiting a paramagnetic behavior, shows a distinct jump and the paramagnetic susceptibility changes across the structural transition.
Ordered olivine-type lithium-cobalt and lithium-nickel phosphates prepared by a new precursor method
Koleva, Violeta,Zhecheva, Ekaterina,Stoyanova, Radostina
, p. 4091 - 4099 (2011/01/08)
Single phases of olivine-type LiCoPO4 and LiNiPO4 were synthesized by thermal treatment of homogeneous lithiummetal-phosphate- formate precursors obtained by freeze drying of aqueous solutions of the corresponding metal formates and LiH2PO4. The structure, thermal behavior, and morphology of the precursors were studied by IR spectroscopy, DTA, and SEM. Cobalt and nickel phosphate-formate precursors have a composition LiMHx(PO4)(HCOO)x-yH 2O, where the formate and phosphate groups are mainly deprotonated. For the Co precursor the formate and phosphates ions are randomly coordinated to both Co and Li cations, for the Ni precursor there is a preferential coordination of the formate and phosphate ions around the Ni2+ and Li+ ion, respectively. Thermal treatment of the precursors yields single phases of olivine-type LiCoPO4 at 450 °C and LiNiPO4 at 700 °C. Structural analysis evidences that both LiCoPO4 and LiNiPO4 have an ordered olivine-type structure without any Li to M disorder between the metal positions and lithiurm deficiency. The effect of the freeze-dried solution concentration and annealing temperature on the structure, crystallite size, and morphology of LiCoPO4 and LiNiPO4 has been discussed. The morphology of the cobalt and nickel phospho-olivines comprises isometric particles with mean sizes of 190 and 380 nm, respectively.