Photoacoustic study of a new neodymium(III) hydrazone complex

The neodymium(III) hydrazone complex [Nd(DBH) 2 (NO 3 ) 3 ] has been synthesized and characterized using microanalysis and IR spectroscopy. High-resolution photoacoustic spectrometry has been applied for studying the complex. The obtained photoacoustic spectrum has been analysed and compared to a similar [Nd(PicBH) 2 (NO 3 ) 2 ]NO 3 complex. The intensities of the f-f transitions in the photoacoustic spectrum of Nd(DBH) 2 (NO 3 ) 3 were two times greater than for the [Nd(PicBH) 2 (NO 3 ) 2 ]NO 3 complex

On the absorption of microwaves by the one-dimensional spin-1/2 Heisenberg-Ising magnet

We analyze the absorption of microwaves by the Heisenberg-Ising chain combining exact calculations, based on the integrability of the model, with numerical calculations. Within linear response theory the absorbed intensity is determined by the imaginary part of the dynamical susceptibility. The moments of the normalized intensity can be used to define the shift of the resonance frequency induced by the interactions and the line width independently of the shape of the spectral line. These moments can be calculated exactly as functions of temperature and strength of an external magnetic field, as long as the field is directed along the symmetry axis of the chain. This allows us to discuss the line width and the resonance shift for a given magnetic field in the full range of possible anisotropy parameters. For the interpretation of these data we need a qualitative knowledge of the line shape which we obtain from fully numerical calculations for finite chains. Exact analytical results on the line shape are out of reach of current theories. From our numerical work we could extract, however, an empirical parameter-free model of the line shape at high temperatures which is extremely accurate over a wide range of anisotropy parameters and is exact at the free fermion point and at the isotropic point. Another prediction of the line shape can be made in the zero-temperature and zero magnetic field limit, where the sufficiently anisotropic model shows strong absorption. For anisotropy parameters in the massive phase we derive the exact two-spinon contribution to the spectral line. From the intensity sum rule it can be estimated that this contribution accounts for more than 80% of the spectral weight if the anisotropy parameter is moderately above its value at the isotropic point.Comment: 23 pages, revtex4-1, 11 figure

Badanie defektów magnetycznych związków NB₂VSBO₁₀ i NB₆VSB₃O₂₅

Introduction and aim: Two new compounds from the Nb-V-Sb-O system will be scrutinized as possible catalysts, because many compounds from this system has showed promising catalytic properties. Since there is often a direct link between the number of defects and catalytic activity of a compound, these two materials will be investigated by magnetic methods to detect existing defects and to determine their structure and properties. Material and methods:NB2VSBO10and NB6VSB3O25 are relatively new compounds synthesized in Department of Inorganic and Analytical Chemistry, West Pomeranian University of Technology, Szczecin. Two magnetic methods have been used - dc magnetisation and electron paramagnetic resonance (EPR) spectroscopy. Results: Although the nominal valences of metal ions in both compounds suggested non-magnetic properties, very complex magnetic response was registered in both magnetisation and EPR measurements. Non-homogeneous distribution of magnetic ions makes possible formation of different types of spin clusters and strongly interacting magnetic subsystems. Conclusion: NB6VSB3O25 seems to be more promising catalyst than NB2VSBO10 as there are more magnetic defects in this compound.Wstęp i cel: Dwa nowe związki z układu Nb-V-Sb-O będą rozważane jako potencjalne katalizatory, gdyż wiele związków z tego układu wykazuje obiecujące właściwości katalityczne. Ponieważ często pomiędzy ilością defektów a aktywnością katalityczną istnieje zależność proporcjonalna, dwa te związki będą badane metodami magnetycznymi aby wykryć istniejące w nich defekty oraz określić ich strukturę i właściwości. Materiały i metody: NB2VSBO10 and Nb6VSb3O25zostały zsyntezowane stosunkowo niedawno w Katedrze Chemii Nieorganicznej i Analitycznej Zachodniopomorskiego Uniwersytetu Technologicznego w Szczecinie. Zastosowano dwie metody badania właściwości magnetycznych - stałoprądową magnetyzację i spektroskopii elektronowego rezonansu paramagnetycznego (EPR). Wyniki: Chociaż nominalna wartościowość jonów metali w obu związkach sugeruje brak magnetycznych właściwości, zarejestrowano bardzo złożoną odpowiedź magnetyczną w pomiarach magnetyzacji i EPR. Niejednorodny rozkład jonów magnetycznych powoduje tworzenie się różnego rodzaju klasterów spinowych i silnie oddziaływujących podukładów magnetycznych. Wnioski: NB6VSB3O25wydaje się być bardziej obiecującym katalizatorem niż NB2VSBO10, ponieważ w tym związku jest dużo więcej defektów magnetycznych

Magnetic interactions in CrSbVO6 studied by EPR

Powder samples of CrSbVO6 were synthesized from a mixture of appropriate oxides by the solid state reaction technique and investigated by the electron paramagnetic resonance (EPR) in the 4-300 K temperature range. At room temperature the EPR spectrum consisted of two widely differing components: a narrow (∼10 mT) line centered at gna = 1.967 and an intense, almost Lorentzian broad (∼100 mT) line at gbr = 1.975. The EPR spectral parameters (linewidth, g-factor, amplitude, integrated intensity) of both components displayed a marked thermal dependence. The temperature dependence of the broad component showed a very interesting behavior - its amplitude increased on cooling from room temperature, reaching a maximum at 50 K and decreased sharply on further cooling. The narrow line in the EPR spectrum of CrSbVO6 was attributed to strongly interacting V4+ and Cr3+ monomers and Cr3+-Cr3+ pairs, while the broad line was due to the V4+-V4+ dimers and spin clusters involving Cr3+ and V4+ ions. © 2008 Elsevier B.V. All rights reserved

FMR line shift for γ-Fe2O3 magnetic nanoparticles embedded in a nonmagnetic matrix

Temperature dependence of the ferromagnetic resonance (FMR) spectra of magnetic nanoparticles or agglomerates of γ-Fe2O3 in nonmagnetic matrixes has been studied. Samples with two types of magnetic nanofillers have been studied: a solid powder and a suspension. Magnetic anisotropy present in the samples allowed analysis of the observed FMR spectrum in terms of two lines arising from the perpendicular (the more intense) and parallel (the weaker) components of the resulting dipolar field. It was observed that the temperature changes of the resonance lines have been effected by the presence of critical phenomena in polymer matrix, especially the freezing processes connected with the arrested movements of certain matrix fragments. A simple model has been put forward to explain partially the shift of the resonance field with the temperature change. It is proposed that an essential part (50%) of the temperature shift of the position of FMR resonance could be caused by change of an effective magnetic moment due to thermal expansion of the matrix. Application of low concentration of magnetic nanoparticles in the polymeric systems, especially possessing extraordinary physical properties, would allow studying them by the FMR method. This might be very helpful for understanding of the critical or exotic phenomena observed in certain materials. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA

Magnetic resonance study of phases in FeVO4Co3V 2O8 system

Multicomponent vanadates Co3xFe4-xV6O 24 have been synthesized using the solid state reaction method from Co3V2O8 and FeVO4.oxides. The electron paramagnetic resonance/ferromagnetic resonance (EPR/FMR) spectra of 20 samples containing solid state phases formed in the FeVO4Co 3V2O8 system have been recorded at room temperature. The howardevansite structure (H-type phase) is produced, which corresponds to the Co2.616Fe4.256V6O 24 formula while a homogeneity range of lyonsite (L-type phase) type structure could be described by the Co31.5xFe4-xV 6O24 formula (0.476<x<1.667). Considering the values of g-factor and linewidth of each registered spectrum the existence of three types of magnetic centers was inferred and correlated with phases detected by XRD method. © 2011 Elsevier B.V. All rights reserved

Parametrization of the Vibronic Contributions to the b40\text{}\text{}_{4}^{0} Spin-Hamiltonian Parameters for 8\text{}^{8}S7/2\text{}_{7}\text{}_{/}\text{}_{2} Ground State Ions in Fluoroperovskites

Parametrization of phonon induced contributions to the experimentally determined temperature dependence of the b$\text{}_{0}^{4}$ spin-Hamiltonian parameter for Gd$\text{}_{3+}$ doped RbCaF$\text{}_{3}$, CsCaF$\text{}_{3}$, RbCdF$\text{}_{3}$ and TlCdF$\text{}_{3}$ single crystals is discussed. Three physically different parametrization schemes are considered, i.e. that of Einstein, Debye and Huang. It is found that the model of Huang, which predicts that the phonon induced contributions should be proportional to the Debye-Waller factor, describes best the experimental data. The method allowing determination of the Debye temperature from EPR data is also suggested

Localized paramagnetic centers in ErxY1-xBa3Cu2O6+y (x=1.0, 0.5) compounds

Oxygen deficient ErxY1-xBa3Cu26+y (x=1.0, 0.5) compounds are studied by EPR spectroscopy. The EPR spectra reveal the presence of high spin (S>1) paramagnetic centers, dimers and free Cu2+ ions, which appear enhanced in the mixed R phase and suppressed in the single R123 one, consistent with phase separation. © 2000 Elsevier Science B.V. All rights reserved

Exchange interactions of ions

The EPR spectrum of (Formula presented) ions in (Formula presented) 0.5) is studied as a function of temperature. In the oxygen-deficient superconducting phase, the (Formula presented) EPR spectrum comprises a broad EPR line described by a rhombic g tensor and anisotropic linewidths along the principal axes. Analysis of the EPR linewidth provides an estimate for the effective isotropic exchange interaction, (Formula presented) between (Formula presented) ions, indicating that the magnetic ordering of the (Formula presented) sublattice is determined by the interplay between the short-range exchange interactions and the long-range dipole-dipole interactions. © 1998 The American Physical Society