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1.
Structure and magnetic properties of a new single-molecule magnet [Mn11Fe1O12 (CH3COO)16(H2O)4].2CH3COOH.4H2O 下载免费PDF全文
A new single-molecule magnet [Mn11Fe1O12 (CH3COO)16(H2O)4]?2CH3COOH?4H2O (Mn11Fe1) has been synthesized.The structure has been studied by the single crystal x-ray diffraction. The difference of Jahn--Teller distortion between Fe3+ and Mn3+ ion reveals that Fe3+ ion substitutes for Mn3+ ion on the Mn(3)
sites in the Mn12 skeleton. The temperature dependence of the magnetization gives a blocking temperature TB=1.9K for Mn11Fe1. Based on the magnetization process analysis of the crystal at T=2K, we suggest that Mn11Fe1 has the ground state with a total spin S= 11/2. 相似文献
2.
R. B. Morgunov V. L. Berdinski A. I. Dmitriev Y. Tanimoto 《Physics of the Solid State》2007,49(5):997-1003
The electron paramagnetic resonance spectra of a molecular magnet synthesized from [Mn12O12(MeCO2)16(H2O)4] high-spin clusters and tetramethyltetrathiafulvalene donor organic molecules are investigated. It is revealed that, in the
temperature range 5–7 K, there appears an additional signal against the background of the ferromagnetic resonance spectrum.
The additional signal consists of a large number of lines and has a resonance nature, because it is observed in the well-reproduced
narrow ranges of the constant magnetic field of the spectrometer (300–650 and 850–1300 Oe) at a frequency of 9.4152 GHz. The
appearance of the additional signal at a temperature of 5 K is attended by a multiple increase in the magnetic susceptibility
of the sample. There is a correlation between the spectral characteristics of the additional signal (such as the average amplitude,
the spectral power, etc.) and the parameters of the ferromagnetic resonance spectrum (the resonance field, the linewidth,
and the integrated intensity). The assumption is made that the additional signal is associated with the magnetic-field-induced
transitions between spin states of Mn12 high-spin clusters for different orientations of crystallites with respect to the external magnetic field.
Original Russian Text ? R.B. Morgunov, V.L. Berdinskiĭ, A.I. Dmitriev, Y. Tanimoto, 2007, published in Fizika Tverdogo Tela,
2007, Vol. 49, No. 5, pp. 945–950. 相似文献
3.
Wen Dong Wei Zhang Yan Ou-Yang Li-Na Zhu Dai-Zheng Liao Kazuyoshi Yoshimura Zong-Hui Jiang Shi-Ping Yan Peng Cheng 《Journal of magnetism and magnetic materials》2007
A Prussian-blue analogue Mn3[Cr(CN)6]2·12H2O has been prepared and characterized by single crystal X-ray analysis and magnetic measurements. The complex has a disordered face-centered cubic lattice and shows two magnetic transition temperatures of 74 and 61 K. 相似文献
4.
M.F. Gerard N.M.C. Casado M. Perec R. Calvo 《Journal of Physics and Chemistry of Solids》2007,68(8):1533-1539
Magnetic and EPR data have been collected for complex [Cu(L-Arg)2](NO3)2·3H2O (Arg=arginine). Magnetic susceptibility χ in the temperature range 2-160 K, and a magnetization isotherm at T=2.29(1) K with magnetic fields between 0 and 9 T were measured. The observed variation of χT with T indicates predominant antiferromagnetic interactions between Cu(II) ions coupled in 1D chains along the b axis. Fitting a molecular field model to the susceptibility data allows to evaluate g=2.10(1) for the average g-factor and J=−0.42(6) cm−1 for the nearest neighbor exchange coupling (defined as Hex=-∑JijSi·Sj). This coupling is assigned to syn-anti equatorial-apical carboxylate bridges connecting Cu(II) ion neighbors at 5.682 Å, with a total bond length of 6.989 Å and is consistent with the magnetization isotherm results. It is discussed and compared with couplings observed in other compounds with similar exchange bridges. EPR spectra at 9.77 were obtained in powder samples and at 9.77 and at 34.1 GHz in the three orthogonal planes of single crystals. At both microwave frequencies, and for all magnetic field orientations a single signal arising from the collapse due to exchange interaction of resonances corresponding to two rotated Cu(II) sites is observed. From the EPR results the molecular g-tensors corresponding to the two copper sites in the unit cell were evaluated, allowing an estimated lower limit |J |>0.1 cm−1 for the exchange interaction between Cu(II) neighbors, consistent with the magnetic measurements. The observed angular variation of the line width is attributed to dipolar coupling between Cu(II) ions in the lattice. 相似文献
5.
Local structural order and temperature-dependent structural variation have been studied in the molecular-based layer ferrimagnet (n-C4H9)4N FeIIFeIII(C2O4)3 by EXAFS and high resolution X-ray powder diffraction. The EXAFS spectra measured at the Fe K-edge are successfully modelled by successive O, C, O and metal shells, showing that even when there is extensive structural disorder due to stacking faults, the local structural order in this class of ferrimagnets is fully retained. In this salt, which shows remarkable negative magnetisation at low temperature (Néel class Q), the EXAFS Debye-Waller factor has a discontinuity at 40 K, corresponding to one found in the magnetisation. At the same temperature there is also a change in the expansion of the lattice as evidenced by the high resolution X-ray powder diffraction. 相似文献
6.
Z. Aloui 《Journal of Physics and Chemistry of Solids》2004,65(5):923-926
Chemical preparation and crystal structure are given for a new cyclotetraphosphate: [3,5-(CH3)2C6H3NH3]4P4O12·3H2O. This compound is triclinic P with the following unit-cell parameters: a=8.298(3), b=8.299(3), c=17.242(7)Å, α=97.13(3), β=102.72(3), γ=64.55(3)°, Z=1 and V=1045.2(8)Å3. The crystal structure has been solved and refined to R=0.040 using 6086 independent reflections. The atomic arrangement can be described as layers organization. Layers built by P4O12 ring anions, ammonium groups and water molecules parallel to the plan (001), between which the organic groups are located. Characterization by X-ray diffraction, IR absorption, and thermal analysis are described. 相似文献
7.
I. Heilmann J.M. Knudsen N.B. Olsen B. Buras J. Staun Olsen 《Solid State Communications》1974,15(9):1481-1484
Thermal decomposition products of the Mohr salt (NH4)2Fe(SO4)2·6H2O have been studied and identified using the Mössbauer effect, X-ray diffraction, infrared spectroscopy, and the gravimetric and thermal differential methods. It has been found that the Mohr salt heated for 96 hr. in air at 520K changes to a single substance identified as NH4Fe(SO4)2 with a single Mössbauer line (width 0.30 mm/sec; isomeric shift 0.30 mm/sec). When the Mohr salt is heated for 1 hr. in air at 770 K it changes to Fe2(SO4)3 with a single Mössbauer line (width 0.33 mm/sec; isomeric shift 0.31 mm/sec) strikingly similar to line of NH4Fe(SO4)2. 相似文献
8.
Fatemeh Mohandes Masoud Salavati-Niasari 《Journal of magnetism and magnetic materials》2010,322(7):872-309
Benzenedicarboxylate complexes, especially phthalate ones, can be significant precursors for the preparation of nano-sized metal and metal oxides. The injection of organic surfactants such as oleic acid (OA) and triphenylphosphine into molecular precursors has yielded samples with size control, narrow size distributions and crystallinity of individual nanocrystals. Fourier transform infrared and X-ray photoelectron spectroscopy revealed that the OA molecules were adsorbed on the ferromagnetic nanoparticles by chemisorption. The temperature-dependent magnetization curve in zero-field-cooled and field-cooled exhibit weak ferromagnetism of the Co3O4 nanoparticles. At 300 K the remanent magnetization is 0.02 emu/g, the coercive field is 441 Oe and the magnetization at saturation is 1.05 emu/g. 相似文献
9.
B. Natarajan 《Journal of Physics and Chemistry of Solids》2007,68(10):1995-2002
EPR spectroscopic investigations on single crystals of diaquabis[malonato(1-)-κ2O,O′] zinc(II) doped with VO(II) ion have been carried out at X-band frequencies and at 300 K. The single crystal, rotated along the three mutually orthogonally axes, has yielded spin-Hamiltonian parameters g and A as: gxx=1.980, gyy=1.972, gzz=1.937 and Axx=8.4, Ayy=6.1, Azz=18.1 mT, respectively. These spin-Hamiltonian parameters reflect a slight deviation from axial symmetry to rhombic, which is elucidated by the interstitial occupation of vanadyl ions. The isofrequency plots and powder EPR spectrum have been simulated. The percentage of metal-oxygen bond has been estimated. The optical absorption spectrum exhibits four bands at 257, 592, 720 and 764 nm suggesting a C4v symmetry. The admixture coefficients and bonding parameters have also been calculated by collaborating EPR data with optical data. 相似文献
10.
Fouad Bentiss Hervé Vezin Elizabeth M. Holt 《Journal of Physics and Chemistry of Solids》2004,65(4):701-705
Using the 2,5-bis(2-pyridyl)-1,3,4-thiadiazole (bptd), we recently prepared [Cu2(bptd) (H2O) Cl4] and [Ni2(bptd)2 (H2O)4] Cl4, 3H2O in which the magnetic centres are connected through one diazine+one chloro and two diazine ligand bridges, respectively. These two compounds are the first examples that show null intramolecular magnetic interactions despite M-M distances close to 3.7 Å within perfectly planar edifices:Down to , [Cu2(bptd)Cl4(H2O)] is paramagnetic while, below Tt, half of the Cu2+ions interact, leading to residual paramagnetism of one Cu2+/f.u. Magnetic susceptibility measurements, EPR and pulsed EPR study indicate the original intermolecular nature of AF exchanges.[Ni2(bptd)2(H2O)4]Cl4·3H2O susceptibility obeys a Curie-law involving pure paramagnetism. Moreover, its EPR spectrum can be interpreted on the basis of virtual S=1 monomers. Below 70 K, Zero Field Splitting (D∼275 G) due to dipolar interactions without magnetic exchanges could be responsible for the LT spectra splitting. For both compounds, the thia role is suggested as partially responsible for the null-in-plane magnetic exchanges. 相似文献
11.
Paul M Forster 《Journal of Physics and Chemistry of Solids》2004,65(1):11-16
A novel layered hydrotalcite-like material, Co7(H2O)2(OH)12(C2H4S2O6), has been prepared hydrothermally and the structure determined using single crystal X-ray diffraction (a=6.2752(19) Å, b=8.361(3) Å, c=9.642(3) Å, α=96.613(5)°, β=98.230(5)°, γ=100.673(5)°, R1=0.0551). The structure consists of brucite-like sheets where 1/6 of the octahedral sites are replaced by two tetrahedrally coordinated Co(II) above and below the plane of the layer. Ethanedisulfonate anions occupy the space between layers and provide charge balance for the positively charged layers. The compound is ferrimagnetic, with a Curie temperature of 33 K, Curie-Weiss θ of −31 K, and a coercive field of 881 Oe at 5 K. 相似文献
12.
We have attempted to characterize the magnetic and electrical properties of a new mixed-metal molecular material {NBu4[Ni(II)0.5Fe(II)0.5Fe(III)(ox)3]}N synthesized by the use of trioxalatoferrate as the building block. Mössbauer spectroscopy was utilized in order to understand local spin structures in this compound. The results indicate that the compound is a semiconducting ferrimagnet with TN=30 K and room temperature conductivity of 6×10−15 Ω−1 cm−1 along with 1.8 eV activation energy under dark. The compound has no appreciable electrical response towards illumination. 相似文献
13.
Lei ZhangYun Hang Hu 《Applied Surface Science》2011,257(8):3392-3398
Both dimethylformamide (DMF) and diethylformamide (DEF) are important solvents for the synthesis of Zn4O(C8H4O4)3 framework (MOF-5). It is generally recognized that DMF molecules can be completely displaced by CH2Cl2 during the synthesis of MOF-5. Herein, however, it was found that the DMF molecules inside the pores of the MOF-5 framework cannot be displaced by CH2Cl2. The desorption of the DMF molecules from the pores, which requires a temperature of 100 °C or above, is the first order with activation energy of 56.38 kJ/mol. In contrast, DEF molecules can be completely displaced by CH2Cl2 during the synthesis of MOF-5, because DEF molecules cannot penetrate into the pores of the MOF-5 paste. 相似文献
14.
Synthesis, crystal structure, and dielectric properties of [C6H4(NH3)2]2ClBiCl6.H2O are reported. The compound crystallizes in the monoclinic system with space group P21/n. The unit cell dimensions are a = 9.836(5), b = 19.582(5), c = 13.082(5) ?, β = 104.731(5)° with Z = 4. The atomic arrangement can be described by an alternation of organic and inorganic layers. The anionic layer is built
up of octahedral of [BiCl6]3- arranged in sandwich between the organic layers. The crystal packing is governed by means of the ionic N–H···Cl hydrogen
bonds, forming a three-dimensional network. The dielectric properties have been investigated at temperature range from 297
to 410 K at various frequencies (10 Hz–100 kHz). Dielectric studies were performed to confirm results obtained with thermal
analysis. The evolution of dielectric constant as a function of temperature and frequency of single crystal has been investigated
in order to determine some related parameters. 相似文献
15.
M.B. Patel 《Solid State Communications》1985,53(4):431-435
Temperature evolution of the infrared spectrum of the title compound confirms the phase transition temperatures 223, 311 and 355 K reported earlier and suggests a new phase transition at 180 K. From the spectral evidence, the transitions below the room temperature (~300 K) are attributed to tumbling motion of the metal aquo-complex, while those above the room temperature are attributed to reorientational motion of the water molecule. The space group in low temperature phases is suggested to be C2s. 相似文献
16.
17.
The thermodynamic properties, spin–lattice relaxation times, T1, and spin–spin relaxation times, T2, of the 27Al, 87Rb, and 133Cs nuclei in MAl(SO4)2·12H2O (M=Rb and Cs) crystals were investigated, and the two crystals were found to lose H2O with increases in temperature. From our results for T1 and T2, we conclude that the discontinuities near Td in the T1 curves of the two crystals correspond to structural changes. In both crystals, below Td the water molecules surrounding the Al3+ and M+ nuclei form distorted octahedra, whereas above Td the water molecules around the Al3+ and M+ nuclei form regular octahedra and the environment of the Al3+ and M+ nuclei has cubic symmetry. Further, the T1 for the 27Al and 87Rb nuclei in RbAl(SO4)2·12H2O below Td were found to increase with increasing temperature, whereas the T1 for the 27Al and 133Cs nuclei in CsAl(SO4)2·12H2O were found to decrease. It is possible that this difference is due to the different characteristics of α- and β-type crystals. 相似文献
18.
The effect of a magnetic field on phase transitions in the Heisenberg ferromagnet Cu(NH4)2Br4·2H2O is investigated. It is found that the singularity shift of the susceptibility χ(P, T) in a magnetic field is approximated by power functions with the indexes ω = 2.5 and ? = 0.58. 相似文献
19.
Chunlong FeiYue Zhang Zhi YangYong Liu Rui Xiong Jing Shi Xuefeng Ruan 《Journal of magnetism and magnetic materials》2011,323(13):1811-1816
CoFe2O4/Fe3O4 nano-composite ceramics were synthesized by Spark Plasma Sintering. The X-ray diffraction patterns show that all samples are composed of CoFe2O4 and Fe3O4 phases when the sintering temperature is below 900 °C. It is found that the magnetic properties strongly depend on the sintering temperature. The two-step hysteresis loops for samples sintered below 500 °C are observed, but when sintering temperature reaches 500 °C, the step disappears, which indicates that the CoFe2O4 and Fe3O4 are well exchange coupled. As the sintering temperature increases from 500 to 800 °C, the results of X-ray diffractometer indicate the constriction of crystalline regions due to the ion diffusion at the interfaces of CoFe2O4/Fe3O4 phases, which have great impact on the magnetic properties. 相似文献