Spectroscopic Study of [(CH₃)₂NH₂][Zn(HCOO)₃] Hybrid Perovskite Containing Different Nitrogen Isotopes

Abstract

We present a combined differential scanning calorimetry (DSC) and infrared (IR), Raman, electron paramagnetic resonance (EPR), and NMR spectroscopy study of dimethylammonium zinc formate frameworks [(CH 3 ) 2 NH 2 ][Zn(HCOO) 3 ] containing 14 N and 15 N nitrogen isotopes. The DSC reveals very small differences in the phase-transition temperatures for both compounds. The IR and Raman spectroscopies indicate different frequencies of the vibrational modes that involve a nitrogen atom. The temperature-dependent IR and Raman spectra also show a tiny isotope effect on the properties and temperature of the phase transition. The EPR measurements are performed for both compounds doped with small amount of paramagnetic Mn 2+ ions. The obtained continuous-wave Mn 2+ EPR spectra of the disordered phase are very similar for both frameworks, whereas the temperature dependence of the zero-field splitting parameter indicates a slightly different distortion of the MnO 6 octahedra in the low-temperature phase. The EPR line width analysis reveals that the activation energy of the (CH 3 ) 2 NH 2 + cation hopping in the disordered phase is 0.21 eV for both compounds. The 15 N NMR spectroscopy measurements of the framework containing the 15 N isotope are used to directly probe this motion. The obtained temperature dependence of the spin−lattice relaxation time is approximated using the same value of the activation energy as determined from the EPR spectroscopy. The negligible nitrogen isotope effect indicates an order−disorder nature of the phase transitions in the investigated compounds.

Quantum dynamics of Mn$^{2+}$ in dimethylammonium magnesium formate

“…[36] for nphoton transitions should have been too heavy to implement and unnecessary. Due to the large zfs expected in this family of compounds 5,12 , only the 1-photon transitions are expected to occur(nphoton transitions are expected when D ∼ h mw 37 with h mw the microwave field ). Using the first order Fermi golden rule, the Rabi frequency of a transition m to n is…”

“…Nevertheless, the crystal field parameters are in the range of what is expected for this family of material. 12 The crystal field distribution ∆D is about 50 MHz, much less than the one needed to simulate the HT phase. In the LT phase, the DMA + cations now have only one possible orientation induced by the ferroelastic phase.…”

“…However, despite this huge effort the precise nature of the phase transition in DMMgF is still obscured. Among many other experimental methods, electron paramagnetic resonance (EPR) spectroscopy is well-suited to study structural phase transitions 4,5,[10][11][12][13] . It used to detect the local environment of a paramagnetic center (e.g., local order parameter such as electric polarization) that can be influenced by the structural transformations.…”

Electronic and optical properties of zinc based hybrid organic-inorganic compounds

“…HOIs have been stabilized with various organic functional groups, such as halides, formates, dyanides, dicyanamides, amides and dicyanometallates [1,7,8]. Ferroelectric properties have been explored for [(CH 3 ) 2 NH 2 ][M(HCOO) 3 ] with M=Mg, Fe, Co, Ni, Cu, or Zn, where polarizations in the range 0.6 μC cm −2 -6 μC cm −2 have been observed [9][10][11][12][13]. The magnitude of polarization is not as high as prototypical ferroelectric oxides, e.g., 50 μC cm −2 and 66 μC cm −2 for Bi 4 Ti 3 O 12 and PbTiO 3 , respectively [14,15], yet might be promising for bio-imaging applications.…”

Stability and flexibility of heterometallic formate perovskites with the dimethylammonium cation: pressure-induced phase transitions

“…We have chosen the DMA + cation due to its wellknown properties in the perovskite-like MOFs with the framework composed of only one type of divalent metal ions. [9][10][11][12][13][14][15][16][17] These studies have revealed plenty of interesting phenomena depending on the metals building the metal-formate framework, including multiferroicity, 9,10,12 ferroelectricity, 16 magnetic 12,13,15 or dielectric 13,14 properties. In the present study we have decided to explore how some properties can be tuned when divalent metal ions are substituted by a mixture of monoand trivalent metal ions in the perovskite-type structure.…”