Magnetic Structures of Heterometallic M(II)–M(III) Formate Compounds

Abstract

A study of the magnetic structure of the [NH(CH)][FeM(HCOO)] niccolite-like compounds, with M = Co (2) and Mn (3) ions, has been carried out using neutron diffraction and compared with the previously reported Fe-containing compound (1). The inclusion of two different metallic atoms into the niccolite-like structure framework leads to the formation of isostructural compounds with very different magnetic behaviors due to the compensation or not of the different spins involved in each lattice. Below T, the magnetic order in these compounds varies from ferrimagnetic behavior for 1 and 2 to an antiferromagnetic behavior with a weak spin canting for 3. Structure refinements of 2 and 3 at low temperature (45 K) have been carried out combining synchrotron X-ray and high-resolution neutron diffraction in a multipattern approach. The magnetic structures have been determined from the difference patterns between the neutron data in the paramagnetic and the magnetically ordered regions. These difference patterns have been analyzed using a simulated annealing protocol and symmetry analysis techniques. The obtained magnetic structures have been further rationalized by means of ab initio DFT calculations. The direction of the magnetic moment of each compound has been determined. The easy axis of the M for compound 1 (Fe) is along the c axis; for compound 2 (Co), the moments are mainly within the ab plane; finally, for compound 3 (Mn), the calculations show that the moments have components both in the ab plane and along the c axis.

A Niccolite Structural Multiferroic Metal–Organic Framework Possessing Four Different Types of Bistability in Response to Dielectric and Magnetic Modulation

“…At LTP, the DEA cations adopt the model II conformation, leading to a low symmetry space group , rather than that of DMA in , since the symmetry of the cation could not be lower than that of the located Wyckoff sites. Thus, besides the impact of metal ions in niccolite structural metal formates, the symmetry of the cation itself should also be taken into account in the total decrease of the symmetry elements during the phase transition. In 1 , along with the phase transition from to , the total number of the symmetry elements of the crystallographic point group decreases from 12 ( E , 2 C 3 , 3 C 2 , i , 2 S 6 , 3σ v ) to 2 ( E , i ) (Figure S4, Supporting Information), suggesting a ferroelastic phase transition with an Aizu notation of 3 mF 1 .…”

Design and Control of Cooperativity in Spin-Crossover in Metal–Organic Complexes: A Theoretical Overview

“…Ferroelectricity and especially multiferroicity in these materials has been extensively studied by Stroppa and coworkers mostly from a DFT based first principles perspective and at times combined with experimental studies [34][35][36][37][38][39][40]. Structural details and effects due to structural phase transitions, strain tuning of various effects like polarisation, and magnetic structure has also been studied by the same groups [41][42][43][44][45]. As mentioned already, the presence of transition metal in these compounds together with its octahedral environment makes them suited also for exhibiting SCO behavior and possibly also cooperativity due to dense nature of framework, which would provide another dimension to functionality of these interesting class of compounds.…”

Pressure dependence of spin canting in ammonium metal formate antiferromagnets

“…16 The degree of spin canting could not be detected from these measurements due to its low value (less than 1 • ). 16,40 The switch in spin direction across the AMF series has also been observed in [(CH 3 ) 2 NH 2 ][M II Fe III (HCOO) 6 ] compounds upon change in the M II cations (Mn 2+ and Co 2+ prefer the ab-plane, and Fe 2+ the caxis), 51 and is related to the change in direction of the anisotropy easy axis for the different M 2+ cations. 51…”