Thermal decomposition of ternary layered hydroxides

Journal of Solid State Chemistry, 1998

The structure of Mn 11 Ta 4 O 21 has been determined and refined using the Rietveld method with combined CuK 1 X-ray and time-of-flight neutron powder data in space group P3 c1 to R F 2 ‫؍‬ 1.3% (neutron data) and R F 2 ‫؍‬ 7.8% (X-ray data). The unit cell is a ‫؍‬ 5.3776(2) A s , c ‫؍‬ 34.040(2) A > , V ‫؍‬ 852.5 A > 3 , and Z ‫؍‬ 2. The structure consists of a 14-layer hexagonal sequence of close packed oxygen atoms and an ordered distribution of metal atoms in octahedral coordination. It can be described as built up of corundum-type Mn 4 Ta 2 O 9 blocks, with six layers of octahedra, alternating with single MnO layers of octahedra. The structure is compared with that of corundum-related Mn 4 Ta 2 O 9 , with unit cell a ‫؍‬ 5.3306(2) A s , c ‫؍‬ 14.336(1) A s , V ‫؍‬ 352.8 A s 3 , and Z ‫؍‬ 2, which has been refined in space group P3 c1 to R F 2 ‫؍‬ 1.9%, using constant-wavelength (‫؍‬ 1.47 A >) neutron powder diffraction data. The magnetic susceptibility of Mn 11 Ta 4 O 21 exhibits a maximum at 23 K and a Curie-Weiss behavior at higher temperatures with a ‫؍‬ ؊240 K and eff ‫؍‬ 5.7 B per Mn atom.

RSC Adv., 2013

In this work we deepen in structural characterization of the recently discovered (C 3 N 2 H 5)[Mn(HCOO) 3 ] metal-organic framework with perovskite-like structure, and we present its magnetic and dielectric properties up to 350 K. At low temperature, the C 3 N 2 H 5 + imidazolium cations, that sit oblique within the cavities of the [Mn(HCOO) 3 ]framework structure, show a cooperative order resulting in an antiparallel arrangement of their electrical dipole moments. Very interestinlgy, it is only above 220 K that thermal energy seems to be able to break this antiferroelectric order, resulting in a linear increase of its dielectric constant with temperature. In addition, this Mn(II) compound is antiferromagnetic below T N = 9 K, with a slightly non-collinear arrangement of its magnetic moments, yielding to a weak ferromagnetism. Therefore, this is a new multiferroic material which exhibits coexistence of magnetic and electric ordering.

Physical Review B, 2012

A theoretical description of the sequence of magnetic phases in Co3TeO6 is presented. The strongly first-order character of the transition to the commensurate multiferroic ground state, induced by coupled order parameters corresponding to different wavevectors, is related to a large magnetoelastic effect with an exchange energy critically sensitive to the interatomic spacing. The monoclinic magnetic symmetry C2 of the multiferroic phase permits spontaneous polarization and magnetization as well as the linear magnetoelectric effect. The existence of weakly ferromagnetic domains is verified experimentally by second harmonic generation measurements.

Inorganic Chemistry, 1988

Four ferrimagnetic chains formed by manganese hexafluoroacetylacetonate and different nitronyl nitroxide radicals 2-R-4,4,5,5-tetramethy1-4,5-dihydro-1H-imidazolyl-1 -oxy 3-oxide (with R = isopropyl, ethyl, methyl, and phenyl) were synthesized. The magnetic susceptibility measurements in the range 6 3 0 0 K show a divergence at low temperature that is compatible with an infinite array structure. The intrachain interaction is antiferromagnetic and estimated by a numerical fit to be in the range 200-330 cm-'. The monodimensionality is confirmed by the X-ray structure of Mn(hfac)*NIT-i-Pr, which crystallizes in the monoclinic P2Jc space group with a = 20.135 (1) A, b = 9.43 (1) A, c = 15.475 (1) A, @ = 110.74 (2)O, and Z = 4. EPR spectra are consistent with the magnetic data and show a behavior typical of low-dimensional materials. The line width in single-crystal spectra of Mn(hfac)zNIT-i-Pr has an angular dependence of the type (3 cos2 0 -1)4'3, while the line shape is intermediate between Lorentzian and Gaussian, showing that the exchange narrowing regime is not attained. (a) University of Florence. (b) Centre $Etudes Nucleaires. Landee, C. P. In Organic and Inorganic Low Dimensional Crystalline Marerials; Delhaes, P., Drillon, M. Eds.; NATO AS1 Series; Plenum: New York, 1987. Gleizes, A.; Verdaguer, M. J. Am. Chem. SOC. 1981, 103, 7373. Gleizes, A.; Verdaguer, M. J . am. Chem. SOC. 1984, 106, 3727. Verdaguer, M.; Gleizes, A,; Renard, J. P.; Seiden, J. Phys. Rev. E: Condens. Matrer 1984, 29, 5144. Verdaguer, M.; Julve, M.; Michalowicz, A,; Kahn, 0. Inorg. Chem. 1983, 22, 2624. Beltran, D.; Escriva, E.; Drillon M. J . Chem. SOC., Faraday Trans. 1982, 78, 1773. Drillon, M.; Coronado, E.; Beltran, D.; Curdy, J.; Georges, R.; Nugteren, P. R.; de Jongh, L. J.; Genicon, J. L. J. Magn. Magn. Mater. 1986, 54-57, 1507. Drillon, M.; Coronado, E.; Beltran, D.; Georges, R. Chem. Phys. 1983, 79, 449. Georges, R.; Curely, J.; Drillon, M. J . Appl. Phys. 1985, 58, 914. Coronado, E.; Drillon, M.; Fuertes, A,; Beltran, D.; Mosset, A,; Galy, J. J. Am. Chem. SOC. 1986, 108, 900. Pei, Y.; Kahn, 0.; Sletten, J. J. Am. Chem. SOC. 1986, 108, 3143. Pei, Y . ; Verdaguer, M.; Kahn, 0.; Sletten, J.; Renard, J. P. Inorg. Chem. 1987. 26. 138. Pei, Y.; Verdaguer, M.; Kahn, 0.; Sletten, J.; Renard, J. P. J . Am. Chem. SOC. 1986, 108, 7428. Landee, C. P.; Djili, A.; Willet, R. D.; Place, H. In Organic and Inorganic Low Dimensional Crystalline Materials; Delhaes, P., Drillon, M. Eds.; NATO AS1 Series; Plenum: New York, 1987.

Inorganic chemistry, 2017

A study of the magnetic structure of the [NH2(CH3)2]n[Fe(III)M(II)(HCOO)6]n niccolite-like compounds, with M(II) = Co(II) (2) and Mn(II) (3) ions, has been carried out using neutron diffraction and compared with the previously reported Fe(II)-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 TN, 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 magnet...

Journal of Physics: Condensed Matter, 2012

Structural, electronic and magnetic properties of TbMn1-xCoxO3 (0.1≤x≤0.9) compounds are reported. Samples are isostructural to TbMnO3 adopting the orthorhombic distorted perovskite structure (Pbnm), except for x=0.4, 0.5 and 0.6, where an ordered double perovskite structure (P21/n) is found. X-ray absorption spectra at the Mn and Co K-edges show an incomplete charge transfer between Mn and Co atoms yielding a mixed valence state Mn 3+ /Mn 4+ and Co 3+ /Co 2+ for the whole series. Neutron powder diffraction measurements show the development of a ferromagnetic ground state for the intermediate compositions (0.3≤x≤0.6) indicating that the ferromagnetic superexchange Mn 4+ -O-Co 2+ interaction is the strongest among a wide set of competitive interactions. The ferromagnetic ordering is, however, not fully achieved and coexists with glassy magnetic properties. With increasing concentration of Co (x≥0.7) the long range ordering vanishes and only a glassy magnetic behavior with slow dynamics is found. These properties could be related to the existence of magnetically inhomogeneous small clusters arising from competitive magnetic interactions.

APL Materials, 2020

Combining ferroelectricity and magnetism in the same material remains a challenge because it involves complex crystal chemistry and stringent symmetry requirements. In conventional ferroelectrics, the polarization arises from the second-order Jahn–Teller effect associated with cations of d0 or s2 lone pair electronic configuration. In contrast, the magnetism arises from cations with partially filled d or f electrons. Materials that incorporate these two kinds of cations in different crystallographic sites exhibit multiferroic properties but with weak coupling between magnetism and ferroelectricity. On the other hand, a strong cross-coupling occurs in some materials, where specific spin structures induce weak ferroelectricity below the magnetic ordering temperature. In this article, we discuss a new class of multiferroics where the polar distortion results from chemical ordering. These polar oxides are mainly pyroelectric in the entire temperature range and exhibit magnetoelectric co...

Journal of Magnetism and Magnetic Materials, 2021

Abstract During the last years, a great attention has been devoted to the discovery of materials that can be used for magnetocaloric applications such as intermetallics and oxides. In this context, the multiferroic TbMnO3 appears as promising magnetocaloric material that can be used for magnetic refrigeration at low temperatures. This multiferroic presents complex electronic and magnetic structures. In this paper, different approaches are used with the aim to get more insight on the driving mechanisms behind the electronic, magnetic and magnetocaloric properties of the TbMnO3 manganite. In this way, a physical model is proposed to describe the magnetic interaction inside this material. Using the density functional theory, the electronic structure, density of states, have been evaluated. The magnetic phase stability and exchange couplings in TbMnO3 have been also investigated in order to understand and to clarify the obscured different magnetic interaction in this compound. Magnetocaloric and magnetic properties have been studied using Monte Carlo Simulation (MCS) within the Ising model. The transition temperatures, the isothermal magnetic entropy change, the adiabatic temperature change and the relative cooling power (RCP) were calculated. The highest obtained isothermal entropy change is found to be -17.8 J/Kg.K for H = 8 T. The RCP maximum value is found to be 507.06 J/Kg and the adiabatic temperature change reaches a maximum value close to 22.5 K in the field change of H = 8 T.

Journal of Physics: Condensed Matter, 2009

Multiferroic manganites of the type RMnO 3 (R=rare-earth) have attracted a great deal of attention due to two main reasons: First, on the technological front multiferroics are promising materials for potential spintronic applications such as four-state memory devices . For their application, however, a better understanding of their fundamental properties is necessary. Second, these materials belong to a class of complex oxides with various coupled ordering phenomena and rich phase diagrams . Generally, RMnO 3 crystallizes in an orthorhombic, perovskite-like structure (space group P nma), if the rare-earth ionic radius is large enough, i.e. r R > r Dy . Thus, the manganites with R = La, Pr, Nd etc. are orthorhombic, whereas the RMnO 3 manganites for R = Y, Tm, Yb, Lu, Er with an ionic radius smaller than that of Dy usually crystallize in hexagonal structure (space group P 6 3 cm). Since the transition between hexagonal and orthorhombic crystal structure of RMnO 3 occurs in the rare-earth series for the ionic radius of Dy or Ho, RMnO 3 with r R r Dy can be synthesized in both structures by applying different growth conditions .

Physical Review B, 2020

We investigated the static and dynamic magnetic properties of the polar ferrimagnet Mn2Mo3O8 in three magnetically ordered phases via magnetization, magnetic torque, and THz absorption spectroscopy measurements. The observed magnetic field dependence of the spin-wave resonances, including Brillouin zone-center and zone-boundary excitations, magnetization, and torque, are well described by an extended two-sublattice antiferromagnetic classical mean-field model. In this orbitally quenched system, the competing weak easy-plane and easy-axis single-ion anisotropies of the two crystallographic sites are determined from the model and assigned to the tetra-and octahedral sites, respectively, by ab initio calculations.