Showing papers on "Debye model published in 1998"

Far-infrared spectra and associated dynamics in acetonitrile-water mixtures measured with femtosecond THz pulse spectroscopy

Abstract: We report the frequency-dependent absorption coefficient and index of refraction in the far-infrared region of the spectrum for mixtures of acetonitrile and water. The mixtures do not behave ideally, and deviate from ideality most noticeably for mixtures that are between 25% and 65% acetonitrile by volume. Two implementations of the Debye model for describing the dielectric relaxation behavior of mixtures are compared, and we show that these mixtures are better treated as uniform solutions rather than as two-component systems. We find an enhanced structure in the mixtures, relative to ideal mixtures, but we do not find direct evidence for microheterogeneity. The Debye time constant for the primary relaxation process for the mixtures is up to 25% longer than that for an ideal mixture.

Elastic moduli of a single quasicrystal of decagonal al-ni-co : evidence for transverse elastic isotropy

Abstract: The single quasicrystal elastic moduli ${c}_{\mathrm{ij}}$ of decagonal Al-Ni-Co were determined using resonant ultrasound spectroscopy at selected fixed temperatures in the range between 5 and 290 K. Decagonal Al-Ni-Co is found to be transversely elastically isotropic to $(0.02\ifmmode\pm\else\textpm\fi{}0.04)%$. The elastic moduli ${c}_{\mathrm{ij}}(T)$ exhibit weak temperature dependences. The elastic Debye temperature ${\ensuremath{\Theta}}_{D}^{\mathrm{el}}$ calculated from ${c}_{\mathrm{ij}}$ measured at 5 K agrees well with the thermodynamic Debye temperature ${\ensuremath{\Theta}}_{D}^{\mathrm{th}}$ obtained from a low-temperature specific-heat experiment.

Phonon density of states of bulk gallium nitride

Abstract: We report the measured phonon density of states of a bulk GaN powder by time-of-flight neutron spectroscopy. The observed one-phonon excitation spectrum consists of two broad bands centered at about 23 and 39 meV corresponding to the acoustic and the first group of optical phonons; two sharp bands of upper optic modes at about 75 and 86 meV; and a gap of 45–65 meV. The phonon dispersion curves, lattice specific heat, and Debye temperature are calculated from fitting the data with a rigid-ion model.

Universal dielectric response of variously doped CeO 2 ionically conducting ceramics

Abstract: The Jonscher power law, or {open_quotes}universal dielectric response{close_quotes} (UDR) behavior was studied for a range of CeO{sub 2} solid solutions with Y{sup 3+} and Gd{sup 3+} dopants, with particular emphasis on dilute systems which possess relatively simple defect structures. The results show power-law frequency dependence of the ac conductivity, with exponent s=0.61{plus_minus}0.03, independent of temperature and concentration. The conductivity data also show scaling behavior in terms of a time constant {tau}, whose activation energy is very close to that of the dc conductivity. For 1{percent} Y and 1{percent} Gd samples, an additional Debye-type relaxation is observed due to dopant{endash}oxygen-vacancy pairs. Such samples are clearly in the association range (stage III). These results contradict the assumption by Almond and West that {tau}{sup {minus}1} is the hopping frequency of the carrier defects. At very low concentrations ({approximately}0.01{percent}), UDR behavior virtually disappears. The present results are then compared to the principal theories that describe UDR behavior. It is found that, while each theory suffers from some drawbacks, the more phenomenological theories fare better. {copyright} {ital 1998} {ital The American Physical Society}

Application of Diffuse Mismatch Theory to the Prediction of Thermal Boundary Resistance in Thin-Film High-Tc Superconductors

Abstract: Thermal boundary resistance (R b ) plays an important role in the design and performance of thin-film high-temperature superconducting devices, such as infrared detectors and optical switches, which rely upon the temperature rise of the film as the basis for their operation. Although there is general agreement on the magnitude of R b from experimental data, there is at present no generally accepted theory. capable of predicting R b for these films, particularly at the intermediate cryogenic temperatures where they are likely to be used. Here, the Diffuse Mismatch Model (DMM), which considers that all phonons reaching the interface between the film and substrate scatter diffusely, is applied to the calculation of R b . The results indicate that when employing the Debye model for the phonon density of states, the DMM yields results slightly more in agreement with data than the Acoustic Mismatch Model (AMM). Considering the measured phonon density of states, however, greatly increases R b over that calculated assuming the Debye model, thus bringing the DMM results in relatively good agreement with the experimental data.

Thermoelastic properties of MgSiO 3 perovskite using the Debye approach

Abstract: MgSiO 3 perovskite is shown to be a Debye-like mineral by the determination of specific heat, C v , entropy, S, and thermal pressure, Delta P Th , using the Debye theory up to 1800 K. Sound velocities and bulk moduli at ambient conditions published by Yeganeh-Haeri were used to find the ambient acoustic Debye temperature, Theta ac D . The variation of Theta ac D with T was assumed to be a curve parallel to the Theta ac D vs. T curves previously found for Al 2 O 3 , MgO, and MgSiO 3 , enabling Theta ac D (T) to be given up to 1800 K. To determine C p , the thermal expansivity, alpha , and the isothermal bulk modulus, K T , are needed. After considering several sets of alpha (T), the alpha (T) data of Funamori and his colleagues were chosen. Using the ambient K T and the values of (theta K T /theta T) P vs. T reported by Jackson and Rigden, K T (T) up to 1800 K was found. Then C P (T) up to 1800 K was found assuming quasiharmonicity in C v . The data behind the C P (T) calculation are also sufficient to find the Gruneisen parameter, gamma (T), and the Anderson-Gruneisen parameters, delta T and delta S , up to 1800 K. The value of q = (theta ln gamma /theta ln V) T was found, and with gamma and rho , Delta P Th vs. V and T was determined. The three sound velocities, v s , v p , and v b = K (sub s/rho ) , were then determined to 1800 K. From v s and v p , Poisson's ratio and the isotropic shear modulus, G, were found to 1800 K. MgSiO 3 perovskite is one of a small, select group of Debye-like minerals for which thermoelastic properties and the equation of state (EOS) are calculable from acoustic data.

Impact of new permittivity measurements on sea surface emissivity modeling in microwaves

Abstract: As part of a measuring program dedicated to the analysis of the dielectric properties of seawater in the frequency range 3–89 GHz, a new dielectric permittivity model based on the standard Debye theory has been developed for remote sensing applications over the ocean below 40 GHz, together with polynomial interpolations at the millimeter frequencies 85.5 and 89 GHz. The aim of this paper is to test the relevance of these new dielectric measurements through statistical comparisons of radiative transfer predictions with satellite and airborne radiometric data between 18 and 89 GHz. A radiometric sensitivity analysis to the permittivity measurement errors is proposed, which yields a sea surface brightness temperature accuracy of at least 0.5 K below 20 GHz, 1 K at 24 GHz, and 1.5 K at 37 and 89 GHz. At frequencies less than 40 GHz, superiority of the revised Debye model is pointed out over the most commonly used model of Klein and Swift [1977]. At millimeter frequencies the new permittivity expressions deviate significantly from the standard Debye predictions, especially at low temperature, suggesting the influence of a second “high-frequency” Debye relaxation. Our comparisons with radiometric data at 89 GHz and in the channel 85.5V of the special sensor microwave imager tend to support this hypothesis. The results emphasize the importance of an adequate modeling of the complex permittivity of seawater as input to the surface emissivity models, at any frequency of the microwave spectrum, and augur interesting outputs in both in-flight calibration and interpretation of satellite data.

An Easy Method for the Determination of Debye Temperature from Thermal Expansion Analyses

Abstract: A combination of the early approaches of the Debye model for specific heat and the Gruneisen theory of the thermal expansion of solids is used to interpolate the thermal variation of lattice parameters. From this analysis, relevant parameters such as the Debye temperature and the value of lattice parameters extrapolated at 0 K are deduced. This method and its limitations are reported. A program has been developed which can be readily used with any computer. Practical applications are given as an illustration. The method is first applied to an ideal cubic compound Na2Ca3Al2F14, which we propose as a standard for thermal expansion calibrations. Then, magnetoelastic phenomena, which occur at very low temperature, are displayed in cubic rare earth garnets by comparison of experimental and extrapolated data. The model is extended to an anisotropic hexagonal system, where the values of lattice parameters extrapolated at 0 K are determined within 10−5. Debye temperatures are estimated within a relative error of 10% and are in good agreement with those calculated from specific heat data; they prove the relevance of this easy method.

Calorimetric study of proton tunneling in solid 5-bromo-9- hydroxyphenalenone and deuteration-induced phase transitions in its deuteroxy analog

Abstract: The heat capacities of 5-bromo-9-hydroxyphenalenone (BHP) and its deuteroxy derivative (BDP) were measured at temperatures between 2 and 310 K. The heat capacity of BHP is a smooth function of temperature and that of BDP has two peaks at 21.3 and 33.9 K. By analyzing the data on BHP, a tunnel splitting of (64±2) cm−1 associated with the quantum mechanical motion of the hydrogen atom in the intramolecular O–H–O hydrogen bond was derived along with the Debye temperature 60.8 K and two Einstein temperatures 131.4 (nondegenerate) and 210.4 K (doubly degenerate). The enthalpy change of 225 J mol−1 and entropy change of 6.8 J K−1 mol−1 were determined for the total thermal effects associated with the two phase transitions in BDP. The value of the transition entropy is consistent with the twofold disorder in the high temperature phase. The tunneling energy and transition enthalpy satisfy an inequality demanded, on the assumption that the potential energies experienced by the proton and deuteron are the same, by ...

Characterization of tin at the surface of float glass

Abstract: Transmission Mossbauer spectroscopy (TMS) and conversion electron Mossbauer spectroscopy (CEMS) have been used to obtain spectra of 119Sn in three commercially produced soda–lime–silica float glasses. Measurements have been made of the f-factor of both tin oxidation states from a series of results at temperatures between 290 and 13 K. TM spectra yielded data on the whole tin layer, which extends to a depth of about 20 μm, while CEM spectra gave information on the near-surface region with a depth of about 2 μm. The isomer shift and quadrupole splitting of Sn4+ in the near-surface were higher than the shift and splitting measured for the whole region, and the Debye temperature, θD, was found to be significantly less in the surface than in the full depth containing tin, showing that it was less tightly bound. The shift, splitting and Debye temperature of Sn2+ remained the same throughout the glass surface within experimental errors. These results are discussed in terms of the conditions of the float process and differences in the coordination number of Sn4+.

Thermal Conductivity of Solid Argon by Classical Molecular Dynamics

Abstract: Following the Green-Kubo formalism in linear response theory, the lattice thermal conductivity of solid argon is determined by using classical molecular dynamics simulation to calculate the heat current correlation function. Comparing the absolute conductivities obtained using the Lennard-Jones potential with experiments, we find the predicted results to uniformly underestimate the measurements in magnitude, whereas the calculated temperature dependence corresponds well with the data. The temporal behavior of the heat current autocorrelation function shows that while a single exponential decay description is appropriate at elevated temperatures, below the half of the Debye temperature, the heat current relaxation clearly consists of two stages, an initial rapid decay associated with local dynamics followed by a slower component associated with the dynamics of lattice vibrations (phonons).

Temperature dependence of the fundamental absorption edge in CuIn3Se5

Abstract: From the study of the temperature dependence of the optical absorption spectra, the energy gap EG of CuIn3Se5 between 10 and 300 K are calculated using the model proposed by Elliot. This variation is compared to the semiempirical relation suggested by Manoogian–Woolley. The Debye temperature ΘD, the dielectric constant e0, and the effective masses of free excitons mex, electrons me, and holes mh are estimated from the analysis of the adjustable parameters of these models.

Mössbauer study of

Abstract: has been studied by means of M?ssbauer spectroscopy and x-ray diffraction. The crystal is found to have a cubic spinel structure with the lattice constant . The iron ions are in ferric states. The temperature dependences of the magnetic hyperfine fields at the nuclei at the tetrahedral (A) and octahedral (B) sites are analysed using the N?el theory of ferrimagnetism. The inter-sublattice superexchange interaction is found to be antiferromagnetic with a strength of while the intra-sublattice superexchange interactions are ferromagnetic with strengths of and . The Debye temperatures of the tetrahedral and octahedral sites are determined to be and , respectively.

Diffraction and rotational transitions in the scattering of D2 from Cu(001) at energies up to 250 meV

Abstract: Absolute diffraction probabilities for the scattering of D2 from a clean Cu(001) surface along the [100] azimuth have been measured at incident kinetic energies between 20 and 250 meV. The measured attenuation of the diffraction intensities with surface temperature corresponds to a surface Debye temperature of ΘD=341 K. The high-resolution angular distributions show clear evidence of rotationally inelastic diffraction (RID) peaks. The RID probability increases with incident energy and represents as much as 30% of the elastic diffraction probability at energies above Ei=200 meV. An Eikonal approximation analysis gives a value h=0.075 A for the surface corrugation which is independent of incident energy. The rotational transition probabilities correspond to an effective value of δ=0.3 for the molecular eccentricity. The experimental results indicate that diffraction of D2 from Cu(001) can be accounted for by a hard-wall collision mechanism over the whole range of investigated energies.

Ab initio single- and multiple-scattering exafs debye-waller factors : raman and infrared data

Abstract: The extended x-ray-absorption fine structure (EXAFS) Debye-Waller factor is an essential term appearing in the EXAFS equation that accounts for the molecular structural and thermal disorder of a sample. Single- and multiple-scattering Debye-Waller factors must be known accurately to obtain quantitative agreement between theory and experiment. Since the total number of fitting parameters that can be varied is limited in general, data cannot support fitting of all relevant multiple-scattering Debye-Waller factors. Calculation of the Debye-Waller factors is typically done using the correlated Debye approximation, where a single parameter (Debye temperature) is varied. However, this procedure cannot account in general for Debye-Waller factors in materials with heterogeneous bond strengths, such as biomolecules. As an alternative procedure in this work, we calculate them ab initio directly from the known or hypothetical three-dimensional structure. In this paper we investigate the adequacy of various computational approaches for calculating vibrational structure within small molecules. Detailed EXAFS results will be presented in a subsequent paper. Analytical expressions are derived for multiple scattering Debye-Waller factors, based on the plane wave approximation. Semiempirical Hamiltonians and the ab initio density functional method are used to calculate the normal mode eigenfrequencies and eigenvectors. These data are used to calculate all single- and multiple-scattering Debye-Waller factors up to a four atom cluster. These ab initio Debye-Waller factors are compared to those calculated from experimental infrared and Raman frequencies. As an example comparison with experimental EXAFS data from ${\mathrm{GeCl}}_{4}, {\mathrm{GeH}}_{3}\mathrm{Cl}$ gases are also reported. Good agreement is observed for all cases tested.

Negative Temperature Coefficient of Electrical Resistivity in B2-Type Ti–Ni Alloys

Abstract: A negative temperature coefficient of electrical resistivity (TCR) has been observed in Ti50-XNi50+X (at.%; X=1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5) in the temperature range between 20 and 350 K. The resistivity vs temperature curve has no hysteresis and the relative resistivity at 20 K (ρ20 K/ρ350 K) decreases with increasing Ni content. X-ray diffraction and magnetic susceptibility measurements show that a negative TCR is not caused by structural phase transition nor by magnetic transition. The Debye temperature of Ti48Ni52, obtained from the analysis of specific heat measurements, is quite low (217 K) and its spin relaxation process has a time duration between 400 µs and 20 ms, suggesting that some lattice instability exists. Based on these results, the origin of a negative TCR is discussed.

Low-temperature elastic coefficients of polycrystalline indium

Abstract: Using an ultrasonic pulse-echo method, we measured the elastic coefficients of polycrystalline indium from 300 to 5 K. All elastic coefficients showed regular temperature behavior, as predicted by an Einstein-oscillator model. The shear and Young moduli showed the largest change, increasing ≈55% during cooling. The Poisson ratio was unusually high at 0.45, just below the theoretical upper bound of 0.5. Using a Marx composite oscillator, we measured the internal friction at room temperature. We calculated the acoustic Debye temperature, 108.4 K, that agreed well with a monocrystal acoustic value, 111.3 K and the specific-heat value, 108.8 K. Also, we calculated the Gruneisen parameters, γL=2.04, γH=2.68, that agreed well with the specific-heat value, γ=2.48 and the shock-wave value, γ=2.24.

Complex Permittivity Spectra of Binary Pyridine–Amide Mixtures Using Time–Domain Reflectometry

Abstract: Frequency spectra of the complex permittivity for pyridine–amide binary mixtures have been determined over the frequency range 10 MHz to 10 GHz, at 5, 15, 25, and 40°C, using the time–domain reflectometry method, for 11 compositions of each pyridine–amide system, e.g., formamide, N-methylformamide, and N,N-dimethylformamide. The relaxation in these systems can be described by a single relaxation time using the Debye model. The static dielectric constant, relaxation time, the corresponding excess dielectric properties, Kirkwood correlation factor, and molar activation energy of the mixtures have been determined. The excess permittivity is found to be positive in the amide-rich region and negative in the pyridine-rich region. The excess inverse relaxation time is negative, except in the pyridine-rich region. The static dielectric constants for the mixtures have been fitted with the modified Bruggeman model. The temperature-dependent relaxation times show the expected Arrhenius behavior.

Ionic transitions and oscillator strengths in Debye plasma - a case study

Abstract: Stability and energy of the excited states of the \(\) ion in plasmas are investigated theoretically using the Debye model. The transition energies of \(\) and \(\) transitions are seen to follow completely opposite trends of variation with the plasma screening strength. The dependence of absorption oscillator strength values on the screening strength is also discussed.

Debye temperature, anharmonic thermal motion and oxygen non-stoichiometry in yttria stabilized cubic zirconia

Abstract: The temperature dependence of the Debye-Waller factors of a 9.4 mol% stabilized cubic ceramic was studied in the range 4-1923 K using neutron powder diffraction. It was found that the data could not be modelled on a harmonic Debye-like model with an additive static disorder component but are significantly anharmonic. The anharmonic thermal motion in this material is not confined to the usual fluorite third-order term for the anion. It is shown that the temperature variation of the Debye-Waller factors is well modelled by an isotropic fourth-order anharmonic vibration of both the cation and anion each with its own additive static disorder component. The Debye temperature was determined as approximately 963 K which is much higher than the only known previous measurement. There is evidence that the sample became non-stoichiometric during the measurements. The oxygen content appears to follow an extrapolation of the lower phase boundary of the Zr-O phase diagram.

Vibrational properties of Pu and Ga in a Pu-Ga alloy from neutron-resonance Doppler spectroscopy

Abstract: We have determined some of the phonon spectral parameters for Pu and Ga in the {open_quotes}stabilized{close_quotes} {delta} phase (fcc) of the Pu-3.6thinspat.thinsp{percent}thinspGa alloy by measuring the Doppler broadening of neutron resonances as a function of temperature. We find the mean phonon energy (first moment of the phonon spectrum) of Pu to be {l_angle}h{nu}{r_angle}=8.22{plus_minus}0.12thinspmeV and the second moment to be {l_angle}(h{nu}){sup 2}{r_angle}=(7.2{plus_minus}0.3){times}10{sup {minus}5}thinspeV{sup 2}. These moments and the value of the ({minus}1)st moment determined from Debye-Waller factors from neutron powder diffraction are consistent with a Debye model with a Debye temperature of 127.2{plus_minus}1.7thinspK. For Ga in the Pu-Ga alloy, {l_angle}h{nu}{r_angle}=16.3{plus_minus}1.4thinspmeV, which is slightly larger than the m{sup 1/2}-weighted value of 15.3 meV expected from the value for Pu (however, the measured value cannot be distinguished from the latter value within experimental error). These results show that Pu-3.6thinspat.thinsp{percent}thinspGa behaves very much like a Debye solid at ambient pressures and low temperature and that the Ga impurity experiences approximately the same (or a slightly stiffer) force field compared with the Pu it replaces. {copyright} {ital 1998} {ital The American Physical Society}

Equation of state of MgSiO3 perovskite and its thermoelastic properties under lower mantle conditions

Abstract: A simple four-parameter model for calculating thermoelastic properties of MgSiO3 perovskite is presented based on the Vinet model for static lattice and the Debye approximation for lattice vibration. The input parameters are the volume of the unit cell, V0, the bulk modulus, K0, its pressure derivative, K0′, and the Debye temperature, Θ0, in the static lattice at zero pressure. For V0, K0 and K0′ the theoretical values by Stixrude and Cohen [1993] are used and Θ0 is determined to reproduce the experimental value at ambient conditions, 980 K, by Akaogi and Ito [1993]. The resulting isobars are in good agreement with experimental data to 1300 K and 11 GPa by Wang et al. [1994], with those to 1200 K at 20 GPa by Utsumi et al. [1995], and with those to 1500 K and to 2000 K, respectively, by Kato et al. [1995] and Funawori et al. [1996] both at 25 GPa. Using the present equation of state together with the method for calculating adiabatic Lame constants λS and μS for isotropic medium given in the present paper, density ρ, and sound velocities νp and νs of MgSiO3 perovskite under lower mantle conditions have been calculated where the constant-entropy model is assumed with the temperature at the core-mantle boundary being taken to be 3000 K. The results for ρ, νp, and νs are in agreement with the preliminary reference Earth model (PREM) within −2.4%∼ −3.7%, +3.3%∼+1.1%, and +0.8%∼−6.8%, respectively, over the lower mantle from 670 to 2891 km in depth. The calculated thermal expansivity under lower mantle conditions is in good agreement with that of the lower mantle estimated by Anderson [1982]. Using the present model with the parameters determined from experimental data at room temperature by Knittle and Jeanloz [1987], assuming Θ0 to be the same as that of MgSiO3 perovskite, thermoelastic properties of (Mg0.9, Fe0.1)SiO3 perovskite under lower mantle conditions have been calculated. The density becomes in much better agreement (+0.4%∼−0.8 %) with PREM and νp and νs remain almost unchanged from those of MgSiO3 perovskite.

Thermodynamic properties of the n-alkanes C19H40 to C26H54 and their binary phase diagrams

Abstract: The shapes of the C22H46-C24H50 and C23H48-C24H50 binary phase diagrams were analyzed. In the C22H46-C24H50 binary system the increased stability of the binary compounds with increasing temperature can be explained by the much larger heat capacity and entropy of the binary compounds compared to that of the components C22H46 and C24H50. In the C23H48-C24H50 system this effect is much less pronounced. The measured enthalpy data of n-alkanes C19H40 to C24H50 and of the binary system C22H46-C24H50 were analyzed to obtain the ‘excess’ heat capacity per atom of carbon {[Cp/(Rm)]-3} (Rm being the number of carbon atoms). The ‘excess’ heat capacity per carbon atom is the value of the heat capacity above the Debye high temperature value of 3R. At low temperatures (below 280 K) one is in the Debye temperature θD region. At higher temperatures the large ‘excess’ heat capacity of the solids explains the movements in the carbon chains. In the liquid the excess heat capacity is small and corresponds numerically to the anharmonic vibrations in low melting metals. In contrast to metals, where the difference in heat capacity between liquid and solid below the melting point is positive Cp(L-s)>0, in the alkanes studied it is strongly negative Cp(L-s)≪0. This explains the shape of the binary phase diagrams C22H46-C24H50, C24H50-C26H54, C22H46-C23H48 and C23H48-C24H50.

Dielectric and pyroelectric response in Nb/semiconducting Y—Ba—Cu—O/Nb structures

Abstract: A study on the dielectric and pyroelectric properties of nonmetallic, polycrystalline Y—Ba—Cu—O thin films was performed for a range of temperatures (170–360K) and frequencies (2 Hz—1kHz). The complex permittivity, as a function of frequency, relaxed according to a first-order Debye Model. This relaxation was shown to be thermally activated, with an activation energy equal to the activation energy for the dc conduction of the material. The behavior of the data indicates that the polarization source is localized carriers near the Fermi level. Pyroelectricity was measured over a temperature range of 170–290 K, showing a constant response over these temperatures. Moreover, the pyroelectric properties of YBCO exhibited a strong sensitivity to poling at elevated temperatures, with a dramatic increase in the magnitude of the response. The pyroelectric coefficient changed from p ≈ 400 nC/(cm2-K) for the unpoled case to p ≈ 20 μC/(cm2-K) after poling with 5000 V/cm for one hour at 320 K.

Crystallization and Mössbauer studies of melt-spun NdFe10.7TiB0.3Nδ alloys

Abstract: Magnetic properties of melt-spun NdFe10.7TiB0.3Nδ ribbons have been investigated as functions of quenching rate and nitriding period. NdFe10.7TiB0.3 were prepared with substrate velocity vs⩽18 m/s and were nitrogenated at 500 °C for 15 min. The NdFe10.7TiB0.3Nδ retains the ThMn12-type tetragonal structure with lattice constants a0=8.640 A and c0=4.811 A, but with an increase in the unit cell volume. The NdFe10.7TiB0.3Nδ was confirmed to have uniaxial anisotropy by x-ray diffraction. Mossbauer spectra were taken at various temperatures ranging from 13 to 855 K. The Curie and Debye temperatures are determined to be Tc=833 K and Θ=390 K, respectively. Each spectrum below Tc was fitted with six subspectra of Fe sites (8i1, 8i2, 8j2, 8j1, 8f, and α-Fe). The area fraction of the subspectra at 13 K are 10.2%, 8.2%, 16.5%, 17.5%, 44.3%, and 3.3%, respectively. The magnetic hyperfine fields for the Fe sites decrease in the order, Hhf(8i)>Hhf(8j)>Hhf(8f).