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Crystallographic and magnetic properties of the double perovskite oxide Ca2FeMoO6 were studied. The single phase polycrystalline Ca2FeMoO6 powder was prepared by a solid-state reaction method. The crystal structure of the Ca2FeMoO6 is found to be monoclinic with lattice constants a0 = 5.4056 A, b0 = 5.5170 A, c0 = 7.6971 A, and β = 89.92°. The Mossbauer spectra have been taken at various temperatures ranging from 17 to Curie temperature (TC) was found to be 350 K. The isomer shift value at room temperature is 0.43 mm/s relative to the Fe metal that are consistent with the Fe3+ valence state. Hyperfine parameters of the Mossbauer spectra were analyzed as a function of temperature and observed the magnetic properties with crystallographic changes through neutron diffraction experiments.

An antianemic medication, Aronamin C Plus, which has simple iron-bearing ingredients, was studied by Mossbauer spectroscopy. The Aronamin C Plus tablet consisted of ferrous fumarate (FeC4H2O4) and other ferric compounds and ferrous phases. A magnetic hyperfine field of ~ 235.7 kOe for ferrous fumarate was measured at 4.2 K. The absorption ratio of ferrous fumarate in Aronamin C Plus was estimated to be ~ 53.1% and those of the ferric and ferrous phases were found to be 22.7% and 24.2%, respectively. 57Fe hyperfine parameters of the studied pharmaceuticals indicated the existence of major ferrous (high-spin, HS) and ferric (low-spin, LS) compounds.

In order to study on the change of magnetic properties according to the tolerance factor, polycrystalline single phase double perovskite oxide Ba2−x;SrxFeMoO6 (x = 0.0, 0.5, 1.0, 1.5, 2.0) are prepared. The crystallographic and magnetic properties have been studied by X-ray diffraction, magnetization measurements and Mossbauer spectroscopy. The Ba2FeMoO6 is analyzed as a cubic structure with Fe3+ and Mo5+ ions ordered at the B-sites. As the x value increases from the cubic structure, the lattice constant decreases more rapidly in the a-b-axis direction than in the c-axis. So that the tetragonal structure starts from x = 1.0. The Curie temperature of the Ba2FeMoO6 and Sr2FeMoO6 were 345 K and 425 K, respectively. As the value of x increases, the Curie temperature increases linearly. In addition, the magnetic hyperfine field fluctuation due to relaxation effects are observed in the Mossbauer spectrum of all series samples.

Sr3Co2Fe24O41 plocrystalline sample was synthesized by using a polymerizable complex method. We investigated the crystallographic and the magnetic properties of sample by using X-ray diffractometer, vibrating sample magnetometer, and Mossbauer spectrometer. Based on the Rietveld refinement, the crystal structure of the sample was found to be single-phased and to be hexagonal with space group of P63/mmc. The hysteresis curves of sample were measured under 15 kOe at various temperatures ranging from 4.2 and 295 K. From the temperature dependence of the magnetization curves under 100 Oe at temperatures between 4.2 and 740 K, three temperature-dependent magnetic transitions were found to have occurred in the Sr3Co2Fe24O41 sample. The Mossbauer spectra of the samples were obtained at various temperatures ranging from 4.2 and 295 K.

Magnetic Fe3−xZn x O4 (x = 0.01, 0.025, 0.050, 0.075, 0.1) nanoparticles are prepared by the high temperature thermal decomposition method. The samples are characterized by using X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), magneTherm device and Mossbauer spectroscopy techniques. From the result of XRD measurement, the crystal structure of Zn-doped Fe3O4 samples are determined to be cubic spinel with space group Fd3m. With increasing Zn contents, x up to 0.050, magnetization and coercivity values at 295 K increase followed by decrement above x = 0.050. Plasma treatment was performed on sample with x = 0.050, showing the highest magnetization values. The magnetization and coercivity values of plasma-treated sample increase to 79.7 emu/g and 5 Oe, respectively. The self-heating temperature of the sample increases up to 70 ◦ C after the plasma treatment. We have analyzed the Mossbauer spectra as three six-line of tetrahedral A-site, octahedral B1, B2-sites and doublet of B3-site at 295 K and four six-line of A, B1, B2, and B3-sites at 4.2 K. From the isomer shift values at 4.2 and 295 K, the valence states at the B2-site is determined to be ferrous and the others are at ferric state. With increasing Zn content, the area ratio of A-site decreases, while the area ratio of B-sites including B1, B2, B3-site increase. It can be seen that the amount of Zn ions substituted at the A- and B- sites affects the super-exchange interaction.

The title compound, C51H48N2O7, was synthesized by the reaction of 25,27-(3,6,9-trioxaundecane-1,11-dioxy)-26,28-(3-phenyl)-3-azapentane-1,5-dioxy)calix[4]arene with tetracyanoethylene in dry DMF. The compound has a 1,3-alternate conformation with an oxo-crown-5 unit and an aza-crown-3 unit with a nitrogen atom connecting tricyanoethylenephenyl group as a chromophore. Pairs of benzene rings of the calixarene are facing one another. Three of the four oxygen atoms connected to a benzene have endo-conformations while the other is exo. The oxo-crown-5 system has a t–g–g–t conformation. The dichloromethane solvent molecule is linked to the main molecule by a C—H...Cl hydrogen bond. In the crystal, C—H...O, C—H...Cl hydrogen bonds and C—H...π(ring) interactions are observed.

The electronic structure change of NiS$_{2-x}$Se$_x$ as a function of Se concentration $x$ has been studied by Ni $L$-edge X-ray absorption spectroscopy (XAS). The XAS spectra show distinct features in Ni $L_3$ edge, indicating whether the system is insulating or metallic. These features can be semi-quantitatively explained within the framework of the configurational interaction cluster model (CICM). In the S-rich region, relatively large charge-transfer energy ($\Delta \sim 5$ eV) from ligand $p$ to Ni 3$d$ states and a little small $p$-$d$ hybridization strength ($V_{pd\sigma} \sim 1.1$ eV) can reproduce the experimental spectra in the CICM calculation, and vice versa in the Se-rich region. Our analysis result is consistent with the Zaanen-Sawatzky-Allen scheme that the systems in S-rich side ($x \leq$ 0.5) are a charge transfer insulator. However, it also requires that the $\Delta$ value must change abruptly in spite of the small change of $x$ near $x$=0.5. As a possible microscopic origin, we propose a percolation scenario where a long range connection of Ni[(S,Se)$_2$]$_6$ octahedra with Se-Se dimers plays a key role to gap closure., Comment: 4 figures

This paper suggests the way to build the integration of internal server by using link server with virtualization method. With the development of on-line games, game communities began to be formed by users, players get fun from playing games, sharing online space with friends, clans, and parties. However, the limit of physical server restrict the allows under average a hundred users to play at same time and place, and three thousand to ten thousand people to access to game community with chat, message, friends functions. By following the explanation of the method from this paper, this limit can be overcome. It will give the function to share information of all connected users in one displayed server. This paper demonstrates the key quality requirements of the server built by this way such as scalable architecture, consistency, and latency is fulfilled.

The temperature variations of the elastic constant C 11 and the corresponding acoustic attenuation coefficient of barium titanate single crystals grown by two different methods in the paraelectric phase were obtained in a wide temperature by means of Brillouin light scattering. Two phenomenological approaches were adopted to attempt to explain the anomalous change in C 11 (denoted as Δ C 11 ) in the paraelectric phase. Δ C 11 exhibited a logarithmic variation as log[( T − T 0 )/ T 0 ] in a certain temperature range from T c to about T c + 80 °C instead of the other variation of ( T − T 0 ) ζ predicted by the mean-field approach. This temperature range was almost the same as the range where precursor dynamics were theoretically predicted to set in. The fact that the logarithmic variation was proposed for uniaxial systems might indicate that the correlated deformation of precursor polar clusters is tetragonal, as was suggested from nuclear magnetic resonance study [7] .

FexTaS2 (x = 0.25, 0.33, and 0.4) was prepared by using a solid state reaction method. The crystallographic structure and magnetic properties of the prepared compounds were investigated by using X-ray Diffraction, superconducting quantum interference device magnetometer, and a Mossbauer spectrometer. The crystal structure of FexTaS2 (x = 0.25, 0.33, and 0.4) was found to be hexagonal with space group P6322. The lattice constants a0 and c0 increase with increasing Fe concentration. The magnetization and the coercivity also increase with increasing Fe concentration. The magnetic transition temperatures of FexTaS2 (x = 0.25, 0.33, and 0.4) were found to be 89, 150 and 47 K, respectively. The Curie-Weiss temperatures of FexTaS2 (x = 0.25, 0.33, and 0.4) were found to be 80, 37, and −82 K, respectively. The isomer shift value of Fe0.33TaS2 at 300 K was 0.68 mm/s relative to the Fe metal, which is consistent with the Fe2+ valence state. The Debye temperature of Fe0.33TaS2 was determined to be ΘD = 486 K.

The ferroelectric phase transition of Ca-substituted barium titanate single crystals, Ba 1− x Ca x TiO 3 (BCTO- x ), with x = 0.12 and 0.20 grown by optical floating zone method were studied by dielectric and Brillouin scattering methods. The X-ray diffraction investigation confirmed the structural phase transition from cubic to tetragonal phase in BCTO- x . The dielectric constant exhibited a sharp peak at the ferroelectric phase transition temperature ( T c ) and a deviation from the Curie–Weiss law on approaching T c from the high-temperature side. Brillouin scattering results showed that, similar to the acoustic properties of BCTO-0.20, dynamic precursor polar clusters are formed in the paraelectric phase of BCTO-0.12 single crystals which interact with acoustic waves via electrostrictive coupling resulting in large acoustic anomalies near T c . However, the temperature dependence of the dielectric constant indicated that diffuseness of the ferroelectric phase transition of BCTO- x became enhanced with Ca content, which was attributed to compositional disorder induced by random substitution of Ba cations by Ca ions.

Single crystalline, , was grown by the floating zone method. The crystal structure was a two-dimensional layered-type rhombohedral($R\

Multiferroic single crystal was prepared using 4-point focused floating zone furnace, and polycrystalline (x

Polycrystalline Y-type barium cobalt ferrite (Ba2Co2Fe12O22; Co2Y) was synthesized using by the conventional ceramic method. At temperatures below 260 K, the crystal structure of Co2Y was determined to be hexagonal with the space group \(R\bar 3m\). It showed a soft ferrimagnetic behavior with Hc = 113 Oe at 297 K and the Neel temperature (TN) was determined to be 615 K. Most of the super-lattice peaks of Co2Y coming from the spin structure decreased with increasing temperature. However, the super-lattice peak at 21.8° increased with increasing temperature at temperatures above 200 K. In addition, we observed a change in the slope of the zero-field cooled magnetization under a low field of 0.01 T at 215 K due to a magnetic structure transition from a helical to a ferrimagnetic spin structure.

In a conventional diffractometer having single monochromator, only one position, parallel position, is used for the diffraction experiment (i.e. detection) because the resolution property of the other one, anti-parallel position, is very poor. However, a bent perfect crystal (BPC) monochromator at monochromatic focusing condition can provide a quite flat and equal resolution property at both parallel and anti-parallel positions and thus one can have a chance to use both sides for the diffraction experiment. From the data of the FWHM and the Δd/d measured on three diffraction geometries (symmetric, asymmetric compression and asymmetric expansion), we can conclude that the simultaneous diffraction measurement in both parallel and anti-parallel positions can be achieved.

The crystalline structure of the ordered perovskite Sr2Fe0.9Cr0.1MoO6 has been determined to be tetragonal at room temperature, with lattice parameters a0=5.578 A and c0=7.866 A. The lattice volume of Cr doped sample was smaller than that of Sr2FeMoO6. Neutron diffraction patterns for the Sr2Fe0.9Cr0.1MoO6 compound have been taken at different temperatures, from 10 to 473 K. The crystal symmetry is cubic ( Fm 3 m ) in the paramagnetic phase and tetragonal(I4/mmm) in the ferrimagnetic phase. The Curie temperature of Cr doped sample is 415 K.

La0.67Pb0.33Mn1−x 57 Fe 1−x O 3 powders were prepared by the sol–gel method and their structural and magnetic properties were investigated with X-ray and neutron diffraction, Mossbauer spectroscopy and vibrating sample magnetometer. Rietveld refinements show that the samples adopt rhombohedral crystal structure with R 3 c symmetry. Mossbauer spectra of La0.67Pb0.33Mn0.99 57 Fe 0.01 O3 have been taken at various temperatures ranging from 14 to 400 K. Temperature dependence of Mossbauer spectra are interpreted with anisotropic hyperfine field fluctuation.

We have investigated the structural and magnetic properties of FeTiTaO6. From the Rietveid-refined XRD patterns of FeTiTaO6, its crystal structure at room temperature is determined to be the rutile structure with lattice constants of α0 = 4.65 Å, and c0 = 3.02 Å. The c/a ratio of 0.649 is almost same as the value in the parent rutile TiO2, which is 0.644. Based on the temperature dependence of the susceptibility between 3 and 400 K, measured with superconducting quantum interference device (SQUID), the magnetic Neel temperature (TN), which is defined as temperature of the maximum slope in dM/dT, is determined to be 40 K. The detailed studies of the local structure have been carried out with 57Co Mossbauer spectroscopy at various temperatures. The Mossbauer spectra of FeTiTaO6 were composed of two six-line hyperfine patterns below 40 K. Also, the magnetic hyperfine field of FeTiTaO6 is found to be 472 kOe at 4.2 K. The Mossbauer spectra clearly reveal the presence of the magnetic ordering below 40 K in FeTiTaO6.

The double perovskite oxide Ba 2 FeMoO 6 has a cubic structure with a 0 =8.0747 A, whereas Sr 2 FeMoO 6 has a tetragonal symmetry with a 0 =5.5729 A and c 0 =7.9077 A. The unit-cell parameters of the strontium compound increase linearly on increasing the temperature, and the crystal symmetry changes into cubic in the paramagnetic phase (above the Curie temperature T C ). Magnetization measurements show a ferrimagnetic behavior for both materials, with T C =345 K for Ba 2 FeMoO 6 and T C =425 K for Sr 2 FeMoO 6 , respectively. As the temperature increases toward T C , Mossbauer spectra show line broadening and 1, 6 and 3, 4 linewidth difference because of anisotropic hyperfine field fluctuation. Temperature dependence of anisotropy energy is calculated from the relaxation rate.

The effects of crystallographic change induced during the annealing process upon the magnetic properties of nanocrystalline Fe78Al4Nb5B12Cu1 alloy were investigated by using x-ray diffraction, Mossbauer spectroscopy, and macroscopic magnetometry. Special focus was concentrated on the structures of interfacial layer, which is a region between nanocrystallite and amorphous matrix. To examine the differences in the crystallographic and the magnetic properties associated with the thermal treatments, amorphous samples were annealed in two different ways, i.e., flash annealing and conventional annealing. The Mossbauer spectra were analyzed to decompose into three or four components, and revised Vincze method was used to extract the distributions of hyperfine parameters. Interfacial layers were found to have a considerable crystalline order. Flash annealing advances the crystallization process earlier than the conventional annealing. As a result, the fraction of the crystalline phase produced by flash annealing ...

Common mathematical theories can have profound applications in understanding real materials. The intrinsic connection between aperiodic orders observed in the Fibonacci sequence, Penrose tiling, and quasicrystals is a well-known example. Another example is the self-similarity in fractals and dendrites. From transmission electron microscopy experiments, we found that FexTaS2 crystals with x = 1/4 and 1/3 exhibit complicated antiphase and chiral domain structures related to ordering of intercalated Fe ions with 2a × 2a and √3a × √3a superstructures, respectively. These complex domain patterns are found to be deeply related with the four color theorem, stating that four colors are sufficient to identify the countries on a planar map with proper coloring and its variations for two-step proper coloring. Furthermore, the domain topology is closely relevant to their magnetic properties. Our discovery unveils the importance of understanding the global topology of domain configurations in functional materials.

We have studied the correlation between the structural distortion and the electronic/magnetic properties in single-crystalline (Lu,Sc)Fe$_2$O$_4$ (Sc=0.05 and 0.3) by using X-ray diffraction (XRD), magnetic susceptibility, and X-ray absorption spectroscopy (XAS)/x-ray magnetic circular dichroism (XMCD)measurements. The Rietveld structure analysis of the XRD patterns revealed that the Sc substitution induced an elongation of the FeO$_5$ bipyramidal cages in LuFe$_2$O$_4$ and increased the Fe$_2$O$_4$ bilayer thickness. A non-negligible decrease in the ferrimagnetic transition temperature T$_C$ is observed in the magnetic susceptibility curve of the Sc=0.3 sample, but the XAS/XMCD spectra do not show any difference except for a small reduction of dichroism signals at the Fe$^{3+}$ absorption edge. We interpret this suppression of T$_C$ to be the result of a decreased spin-orbit coupling effect in the Fe$^{2+}$ $e_{1g}$ doublet under $D_{3h}$ symmetry, which is induced by the weakened structural asymmetry of the FeO$_5$ bipyramids., Comment: 13 pages, 5 figures

We synthesized single crystals of TiSe 2 with various Cu concentrations, and have performed an angle-resolved photoemission spectroscopy (ARPES) study in order to understand the CDW mechanism and to reveal the role of the Cu atoms in Cu-doped 1T-TiSe 2 . The measurements reveal that during the well-known charge density wave (CDW) transition the pristine TiSe 2 sample undergoes a transition from a very small indirect gap semiconductor to a larger one. No nesting sign was observed in the Fermi surface in the CDW phase. The transition is suppressed in the Cu-doped samples, and an electron pocket appears near the L point, which may help appearance of the superconductivity of Cu x TiSe 2 through the BCS–Eliashberg relation.

The crystallographic and magnetic properties of TbFeO3 powder were characterized by X-ray diffraction, Mossbauer spectroscopy, and magnetic moment measurement techniques. Also, the change of phase transition was observed with differential thermal analysis (DTA). From the Mossbauer spectroscopy results, isomer shift values at room temperature and 4.2 K are in the range of 0.25–0.36 mm/s, which means that the valence state of Fe ions is ferric (Fe3+). The Neel and Debye temperatures are determined to be TN=692 K and Θ=337 K, respectively. The magnetic moment rapidly decreases with increase in temperature up to 250 K. Above 250 K, it starts increasing and shows a convex maximum. After its maximum value about 350 K, it eventually reaches to zero. The inflection points in the M–T curve are in accord with the exothermic peaks from heat capacity measurement results and magnetic hyperfine field anomaly from the Mossbauer spectroscopy results. Using the Mossbauer technique we suggest that the convex curve arises from minute spin canting, in the antiferromagnetically ordered state of the slightly distorted perovskite structure.

The ferrimagnetic and piezoelectric materials GaFeO 3 were prepared by slow cooling and quenching method, and studied by X-ray diffraction, neutron diffraction and Mossbauer spectroscopy. The crystal structures of samples were found to be orthorhombic with the lattice constants of the slowly cooled sample a = 8.7457 , b = 9.3921 , and c = 5.0816 A , and those of the quenched sample a = 8.7462 , b = 9.3896 , and c = 5.0809 A . The different behaviours of magnetic structure between two samples appeared by Mossbauer measurement. For the quenched sample, Neel temperature was 210 K, while it increased to 260 K for the slowly cooled sample. The decrease of magnetic transition temperature originates from distributions of magnetic Fe ion at four cation sites and the strength of exchange interaction between magnetic ions.

The crystallographic and magnetic properties of YMn 1.8 Fe 0.2 O 5 powders have been studied by X-ray, neutron diffraction, and Mossbauer spectroscopy. The samples were prepared by sol–gel process and crystallized at various temperatures. The crystal structures of the powders sintered below 1100 °C were found to be a single phase of orthorhombic (pbam), whereas the other samples sintered above 1200 °C were changed to hexagonal structure with satellite phases. The Mossbauer spectra of YMn 1.8 Fe 0.2 O 5 powders can be understood primarily owing to its chemical and structural complexities.

X-ray and neutron diffraction, Mossbauer spectroscopy, and vibrating sample magnetometer have been used in order to study the structural and magnetic properties of the La 0.67 Pb 0.33 Mn 1−x 57 Fe x O 3 perovskite compounds. Samples were fabricated using the sol–gel method. As the temperature increases toward TC, Mossbauer spectra of La 0.67 Pb 0.33 Mn 0.99 57 Fe 0.01 O 3 show line broadening and the difference between 1, 6 and 3, 4 linewidths because of anisotropic hyperfine field fluctuation. Temperature dependence of anisotropy is calculated from the relaxation rate.

We have studied effects of the partial substitution of La/sup 3+/ for A/sup 2+/ on the magnetic properties of double perovskites A/sub 2/FeMoO/sub 6/ (A=Ca and Ba). Polycrystalline A/sub 2-x/La/sub x/FeMoO/sub 6/ (0/spl les/x/spl les/0.3) samples have been prepared by the conventional solid-state reaction in a stream of 5% H/sub 2//Ar gas. The X-ray data indicate that A=Ca is monoclinic with the space group P2/sub 1//n and A=Ba is cubic with the space group Fm3m. The substitution of La/sup 3+/ for A/sup 2+/ results in a cell volume increase for A=Ca and a cell volume reduction for A=Ba. Saturation magnetization, which is 3.5 /spl mu//sub B//f.u. for undoped A=Ca (x=0) and 3.9 /spl mu//sub B//f.u. for undoped A=Ba (x=0), decreases with increasing x. This decrease of magnetization arises from the reduction of moment associated with the electron doping and the disorder at the Fe and Mo sites. The partial substitution of La/sup 3+/ for Ba/sup 2+/ considerably enhances the Curie temperature T/sub c/ from 316 K for x=0 to 334 K for x=0.2. However, the T/sub c/ in Ca/sub 2-x/La/sub x/FeMoO/sub 6/ is not enhanced significantly with increasing x.

The double perovskite Ba 2 FeMoO 6 has been studied by Mossbauer technique, neutron and X-ray diffraction. The structure is found to be cubic with lattice constant a 0 =8.0747 A. As the temperature increases towards the Curie temperature, T C =345 K, Mossbauer spectra show the line broadening and the difference between 1, 6 and 3, 4 line width because of anisotropic hyperfine field fluctuation. The anisotropic field fluctuation of +H (P + =0.85) was greater than that of –H (P – =0.15 ). We also calculated the frequency factor and temperature dependence on anisotropy energy from the relaxation rate.

The iron-doped perovskite La 0.67 Sr 0.33 Mn 0.99 57 Fe 0.01 O 3 compound has been studied by X-ray diffraction, Mossbauer spectroscopy, and vibrating sample magnetometry. The single phase of the polycrystalline La 0.67 Sr 0.33 Mn 0.99 57 Fe 0.01 O 3 powder has been prepared by a water-based sol-gel method. Crystalline La 0.67 Sr 0.33 Mn 0.99 57 Fe 0.01 O 3 was a rombohedral structure with lattice parameters a 0 = 5.480 A, α = 60.259°. Mossbauer spectra of La 0.67 Sr 0.33 Mn 0.99 57 Fe 0.01 O 3 have been taken at various temperatures ranging from 20 to 400 K. Analysis of 57 Fe Mossbauer spectrum has considered anisotropic hyperfine field fluctuation. Temperature dependence of anisotropy energy is calculated from the relaxation rate.

Some effects of Fe/Mo disorder on magnetic and electrical properties in Ba 2 Fe 1+ x Mo 1− x O 6 have been investigated. As x increases from 0 to 0.5, saturation magnetization decreases from 3.5 to 1.8 μ B /f.u. with increasing of coercivity as well as remanence. The magnitude of magnetoresistance decreases from 26% for x =0 to 15% for x =0.5 with magnetic fields of 0.7 T at 20 K.

The effects of crystallographic change induced during annealing process upon the magnetic properties of nanocrystalline Fe 83 B 9 Nb 7 Cu 1 alloy were investigated by using Mossbauer spectroscopy. Special focus was concentrated on the structures of interface (IF) layer, which is a region between a nanocrystalline and amorphous matrix (AM). As-quenched amorphous ribbons were flash annealed in temperature range between 623 and 823 K to obtain different stages of crystallization. Revised Vincze method was used to extract the distributions of hyperfine parameters. Mossbauer spectra consist of both sharp sextet due to BCC–Fe phase and three binomially distributed sextets due to AM, the diffused region (DR) and IF layer, respectively. By examining the distributions of hyperfine parameters, DR in which magnetic interactions diffused out to AM could be singled out.

We have investigated low-field magnetoresistance (MR) and magnetic properties of Ba/sub 2/Fe/sub 1+x/Mo/sub 1-x/O/sub 6/ (x=0-0.2) to point out some effects of Fe-Mo disorder between the Fe and Mo ions. Polycrystalline samples have been prepared by the conventional solid-state reaction in a stream of 5% H/sub 2/-Ar gas. X-ray data indicate that the symmetry is cubic and the data are compatible with the Fm3m space group. All samples are single phase and exhibit a series of superstructure-reflection lines due to cation order of Fe and Mo. The magnitude of the negative MR is 2.9% for x=0 and 1.5% for x=0.2 at room temperature with magnetic fields of 7 kOe. Saturation magnetization is 2.8 /spl mu//sub B//f.u. for x=0.2 which is smaller than the value of 3.8 /spl mu//sub B//f.u. for x=0. This large variation of magnetization between x=0 and 0.2 arises from the disorder at the Fe and Mo sites.

The gas-microphone photoacoustic (PA) technique has been applied to determine the second-order phase transition in manganite compounds La 1− x Ca x MnO 3 ( x =0.1 and 0.2). A comparative analysis of the PA result with magnetization and electrical resistivity measurements has been performed. The doping of Ca causes the occurrence of ferromagnetic (FM) ordering. The FM transition temperature T c , determined from magnetization measurement, is 145 and 180 K for x =0.1 and 0.2, respectively. The temperature at which the anomaly of PA signal occurs is consistent with T c determined from the magnetization measurement. The change of PA signal arises at the same temperature in both cases with decreasing and increasing temperatures. This implies that the paramagnetic to FM phase transition can be regarded as a second-order phase transition with no latent heat at T c .

We investigated the magnetic nature of Fe(1/4)TaS2 using x-ray absorption spectroscopy, photoemission spectroscopy, and first principles band calculations. The results show a large unquenched orbital magnetic moment (∼1.0 μ(B)/Fe) at intercalated Fe sites, resulting in a gigantic magnetic anisotropy (H(A)≃60 T). The magnetic coupling is well understood in terms of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, suggesting a novel RKKY ferromagnet with Ising-type spin states. We also found that this indirect exchange coupling between the neighboring Fe spins is ferromagnetic and maximized at the Fe-Fe distance of 2×2 superstructure.

A strong relaxation mode was observed in the gigahertz frequency window in the paraelectric phase of Ba₀.₈₀Ca₀.₂₀TiO₃ single crystals by using Brillouin light scattering. The appearance and growth of this relaxation mode were accompanied by substantial softening of the longitudinal acoustic mode as well as a remarkable increase in the hypersonic damping. Similar to BaTiO₃, the temperature dependence of the relaxation time of Ba₀.₈₀Ca₀.₂₀TiO₃ displayed a slowing-down behavior near the Curie temperature, indicating the order-disorder nature of the paraelectric-ferroelectric phase transition in this substance. The dynamics of precursor polar clusters observed in this work was discussed in relation with recent theoretical studies and found to be consistent with their predictions.

We investigated the magnetic nature of Fe(1/4)TaS2 using x-ray absorption spectroscopy, photoemission spectroscopy, and first principles band calculations. The results show a large unquenched orbital magnetic moment (∼1.0 μ(B)/Fe) at intercalated Fe sites, resulting in a gigantic magnetic anisotropy (H(A)≃60 T). The magnetic coupling is well understood in terms of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, suggesting a novel RKKY ferromagnet with Ising-type spin states. We also found that this indirect exchange coupling between the neighboring Fe spins is ferromagnetic and maximized at the Fe-Fe distance of 2×2 superstructure.

Based on the detailed Mn L{sub 2,3}-edge x-ray resonant scattering results, we report a new complexity in the magnetic order of multiferroic orthomangnites, which has been considered as the simple A-type cycloid order inducing ferroelectricity. The Dzyaloshinskii-Moriya interaction involved in the orthorhombic distortion brings on F-type canting from the A type, and the ordering type becomes the off-phase synchronized bc cycloid in TbMnO{sub 3} or the tilted antiphase ab cycloid in Eu{sub 3/4}Y{sub 1/4}MnO{sub 3}. The F-type canting is responsible for the magnetic field-driven multiferroicity to weak ferromagnetism transition.