Showing papers on "Curie–Weiss law published in 1999"
TL;DR: In this article, a thermodynamic theory is used to calculate the dielectric properties of epitaxial thin films grown on cubic substrates imposing biaxial tension on the film prototypic cubic state.
Abstract: A thermodynamic theory is used to calculate the dielectric properties of epitaxial thin films grown on cubic substrates imposing biaxial tension on the film prototypic cubic state. For such “tensile” substrates, the theory shows that, in a conventional plate–capacitor setup, the films should display only a monotonic variation or a broad maximum in the temperature dependence of the permittivity and an apparent absence of the hysteretic polarization behavior. Changes of the Curie–Weiss temperature and constant caused by the mechanical film/substrate interaction are also predicted. Theoretical results agree with the observed properties of columnar-structured BaTiO3 and SrTiO3 thin films grown on Si.
135 citations
TL;DR: In this paper, a field-induced transition is observed in the paramagnetic state, which corresponds to a doubling of the cluster size and an increase of the strength of the interaction between them.
Abstract: The susceptibility of ~Sm0.65Sr0.35!MnO3 shows an unusual temperature dependence above the Curie temperature which is attributed to the presence of small manganese-ion clusters with S'9. A field-induced transition is observed in the paramagnetic state, which corresponds to a doubling of the cluster size and an increase of the strength of the interaction between them. The continuous transition from small to large clusters is interpreted in terms of electron phase segregation in a two-phase region. Magnetic hysteresis in the paramagnetic state is ascribed to potential fluctuations due to Sr substitution. Magnetoresistance measurements correlate with the magnetic measurements by showing a change of regime from quadratic to linear in field when the magnetic transition is induced. Thermal hysteresis of about 8 K in the magnetization and resistivity around the Curie temperature (TC5120 K) is also related to the existence of the two paramagnetic phases. @S0163-1829~99!07741-3#
74 citations
TL;DR: The hexagonal perovskite solid solution Ba 1− x Sr x CoO 3 (0≤ x ≤05) was synthesized by treatment of cubic perovsite precursors at 500°C in high pressure oxygen as discussed by the authors.
72 citations
TL;DR: In this paper, a new ternary filled skutterudite, YbFe4Sb12, was synthesized by reaction sintering and the crystal structure was determined from single crystal X-ray counter data: LaFe4P12-type, space group Im 3 −T h 5 No. 204, Z=2, a=0.91571(5)nm.
67 citations
TL;DR: In this paper, three different environments were observed for the paramagnetic anions with two in a stacking mode and one approximately orthogonal to the stack, the stacking showed an ACA-type repeat unit with an inversion center on complex C. Magnetic susceptibility measurements show Curie-Weiss behaviour with a change in parameters at around 50 K.
Abstract: [Ethylpyridinium][Ni(mnt) 2
] has been prepared by electrochemical oxidation of the corresponding dianionic salt. The X-ray structure has been determined. Three different environments were observed for the paramagnetic anions with two in a stacking mode and one approximately orthogonal to the stack. The stacking showed an ACA-type repeat unit with an inversion centre on complex C. Magnetic susceptibility measurements show Curie-Weiss behaviour with a change in parameters at around 50 K. Above this temperature a Curie constant of 0.3 emu K mol
–1
and a Weiss constant of –150 K were observed and below 50 K these values were 0.08 emu K mol
–1
and +2 K respectively. A maximum in the susceptibility was observed at 285 mK which suggests low temperature ordering to a phase with a non-cancelled alignment of the spins. Intermolecular interactions and the effect of temperature were assessed in terms of transfer integral calculations.
61 citations
TL;DR: In this paper, the lattice constant, dc resistivity, dielectric constant, saturation magnetization and Curie temperature were studied on a series of Cr-substituted Li-Sb ferrite systems.
Abstract: The lattice constant, dc resistivity, dielectric constant, saturation magnetization and Curie temperature were studied on a series of Cr-substituted Li-Sb ferrite systems. The dc resistivity increases with increase of the chromium level. A change in slope was observed in the variation of resistivity with temperature and hence two regions of different activation energy. The study of dielectric permittivity with frequency showed dispersion for the whole system. The saturation magnetization and the Curie temperature were found to decrease with increase of the substitution level.
50 citations
TL;DR: In this paper, the core-level binding energies of O 1s, B 1s and Fe 2p have been measured with both O 1 s and B 1 s peaks shifting by about 2 eV towards smaller binding energies in the Fe-containing borate glasses while the 2p 3/2 and 2p 1/2 core levels for the glasses remain essentially unchanged from those of Fe2O3 powder.
Abstract: Iron–sodium borate glasses with the chemical composition [(B2O3)0.70−x(Na2O)0.3(Fe2O3)x], where 0.00⩽x⩽0.15, have been prepared and investigated by X-ray photoelectron spectroscopy (XPS) and magnetization measurements. The core-level binding energies of O 1s, B 1s, and Fe 2p have been measured with both O 1s and B 1s peaks shifting by about 2 eV towards smaller binding energies in the Fe-containing borate glasses while the Fe 2p3/2 and 2p1/2 core levels for the glasses remain essentially unchanged from those of Fe2O3 powder. The O 1s spectrum is deconvoluted into two peaks and the variation in the ratio of the peak areas is discussed in terms of the local iron structure. We suggest that both X-ray photoelectron spectroscopy and magnetization measurements show that the Fe ions remain essentially in one oxidation state, probably Fe3+, for the Fe borate glasses. In addition, the appearance of a large hysteresis between the zero field-cooled and field-cooled magnetization data indicate that the Fe moments are clustered and that the predominant interaction is antiferromagnetic.
48 citations
TL;DR: In this paper, magnetization and electron-spin-resonance (ESR) measurements around the Curie temperature on single-crystal and ceramic colossal magnetoresistance manganites were reported.
Abstract: We report magnetization and electron-spin-resonance (ESR) measurements around the Curie temperature on single-crystal and ceramic colossal magnetoresistance manganites. The temperature dependence of the ESR linewidth below $\ensuremath{\approx}{1.1T}_{C}$ is well described in terms of a two-magnon scattering relaxation mechanism induced by the demagnetization fields of the pores between crystallites.
45 citations
43 citations
TL;DR: The self-fluxing Al71Pd21,Mn8 quasicrystals have been grown from the ternary melt via a selfflux technique.
Abstract: Icosahedral Al71Pd21,Mn8 quasicrystals have been grown from the ternary melt via a ‘self-flux’ technique. The nucleation is exceptionally well controlled, and individual grains can have masses of up to almost 30 g (limited only by the dimensions of the growth crucible). The quasicrystals grown by this technique are readily separated from the melt by decanting and clearly manifest a dodecahedral morphology with pentagonal facets. X-ray and electron-diffraction data indicate a remarkably well-ordered structure. with a correlation length of over 1000 A. The magnetic susceptibility has a temperature-independent diamagnetic component and a temperature-dependent paramagnetic term. For temperatures greater than approximately 60 K, the paramagnetic term follows a Curie-Weiss temperature dependence characterized by an average effective moment of 0.62 ± 0.02μB/Mn and a Weiss temperature of −12.8 ± 0.1 K. Deviations from the Curie-Weiss temperature dependence for temperatures less than approximately 60 K ma...
39 citations
TL;DR: In this article, temperature-dependent magnetization and susceptibility measurements in situ in UHV were performed to study the ferromagnetic properties of Co/Cu(0, 0, 1) at the transition from islands to closed layer growth.
TL;DR: In this paper, the magnetic properties of Ho@C82 and Gd@C 82 were characterized in the temperature range of 1.8−100 K with an applied magnetic field up to 5 T.
Abstract: Magnetic properties of Ho@C82 and Gd@C82 were characterized in the temperature range of 1.8−100 K with an applied magnetic field up to 5 T. The isothermal magnetization curves of Gd@C82 and Ho@C82 follow the Brillouin function down to 8 and 12 K, respectively. Unlike Gd@C82, the fitting to the Curie−Wiess law for Ho@C82 results in an effective magnetic moment which is significantly smaller than that of a free Ho3+ ion. The magnetic moment reduction and the imperfect paramagnetic behavior of Ho@C82 are ascribed to the carbon cage crystal field effect, the partial hybridization of the orbitals of the entrapped Ho atom and the carbon cage, and the interactions between the metal centers.
TL;DR: In this paper, the authors investigated the magnetic and optical properties of potassium clusters incorporated in zeolite LTA at loading densities of K atoms between 3.5 and 7.2 per cluster.
Abstract: Magnetic and optical properties are investigated for potassium clusters incorporated in zeolite LTA at loading densities of K atoms between 3.5 and 7.2 per cluster, the latter of which is saturated. The Curie–Weiss law with negative Weiss temperature -35 K is seen at 3.5 atoms per cluster, and gradually approaches the Curie law as the loading density increases up to 7.2 atoms per cluster. The Curie temperature, ∼8 K at 3.5 atoms per cluster, approaches 0 K at 7.2 atoms per cluster. These results suggest that the antiferromagnetic coupling between localized magnetic moments of K clusters decreases with increasing K-loading density, and almost disappears at the K-loading density of 7.2 atoms per cluster. The insulator-like absorption tail is observed in the infrared region at any loading density, indicating that K clusters in LTA are in the Mott insulator phase. The average magnetic moment estimated from the saturation magnetization remarkably increases from 0.25 to 0.75 μB per cluster as loading density increases from 3.5 to 7.2 atoms per cluster. On the contrary, the average magnetic moment estimated from the Curie constant is ∼1.6 μB per cluster, and almost independent of the loading density. The explanation of these magnetic properties by the model of ferrimagnetism proposed in a previous paper proves difficult.
TL;DR: The structural and magnetic properties of Gd3(Fe1−xCox)25Cr4 compounds with x = 0.6 have been investigated in this paper, and the structures of all the compounds investigated are found to possess monoclinic symmetry and belong to the A2/m space group.
Abstract: The structural and magnetic properties of Gd3(Fe1−xCox)25Cr4 compounds with x=0–0.6 have been investigated. The structures of all the compounds investigated are found to possess monoclinic symmetry and belong to the A2/m space group. Substitution of Co for Fe leads to a clear contraction of the unit-cell volume. The Curie temperature increases from 492 K for x=0 to 762 K for x=0.6. The composition dependence of the saturation magnetization at 5 K reaches a maximum around x=0.3. It is noteworthy that substitution of Co for Fe results in a significant change of the magnetocrystalline anisotropy of the Co sublattice, and changes the easy magnetization direction of Gd3(Fe1−xCox)25Cr4 compounds from basal plane to easy axis.
TL;DR: The effects of structural, electrical and magnetic properties with the isovalent chemical substitution of Ca2+ into the Sr2+ sites in La12(Sr18−xCax)Mn2O7 (x=0-08) are investigated in this paper.
Abstract: The effects of structural, electrical and magnetic properties with the isovalent chemical substitution of Ca2+ into the Sr2+ sites in La12(Sr18−xCax)Mn2O7 (x=0–08) are investigated The highest magnetoresistance ratio [ρ(0)/ρ(H)] of 208% (H=15 T) at a temperature of 102 K was observed for the x=04 sample The Curie temperatures decreased from 135 to 102 K for x=0–04, respectively Moreover, the Weiss constants θ were varied from the positive to negative value with increasing Ca concentration The antiferromagnetic behavior with Neel temperature around 30 K was found in the x=08 sample The magnetization measurements show that the hysteresis phenomenon appeared at the temperatures below the Curie or Neel temperatures
TL;DR: In this paper, the xHo2O3-Na2B4O7 glass system (0≤x≤0.20) was studied by magnetic susceptibility, density and IR spectroscopic measurements.
Abstract: The xHo2O3–(1−x)Na2B4O7 glass system (0≤x≤0.20) was studied by magnetic susceptibility, density and IR spectroscopic measurements. Magnetic susceptibility data suggest the presence of Ho3+ions both as isolated and exchange coupled species. IR and density measurements give evidence of the network modifier role played by the holmium ions in these glasses.
TL;DR: In this paper, it was shown that the permanent magnetic field formed by the synthesis of ferromagnetic materials depended on the difference between the combustion temperature and the Curie temperature of the product and was most likely generated by chemoionization processes generated by the moving high-temperature reaction zone.
Abstract: We report here the observation of chemomagnetism, generation of a magnetic field by rapid high-temperature solid reactions producing various oxides. The low-level transient magnetic fields were measured with a high-Tc superconducting quantum interference device magnetometer during the synthesis of both nonferromagnetic and ferromagnetic (ferrite) compounds. The magnetic field was most likely produced by chemoionization processes generated by the moving high-temperature reaction zone. The permanent magnetic field formed by the synthesis of ferromagnetic materials depended on the difference between the combustion temperature and the Curie temperature of the product.
TL;DR: In this article, the electrical resistivity ρ and the magnetic susceptibility χ were measured for the sintered samples of Ca 1- x La x RuO 3 (0≦ x ≦1) (La x ) and Ca 1 - x Pr x Ru O 3 (x ≦0.2).
Abstract: The electrical resistivity ρ and the magnetic susceptibility χ were measured for the sintered samples of Ca 1- x La x RuO 3 (0≦ x ≦1) (La x ) and Ca 1- x Pr x RuO 3 ( x ≦0.2). The temperature coefficient dρ/d T is positive at 300 K for all the samples, but ρ increases logarithmically with decreasing temperature as for the Kondo effect except for the end members x =0 and 1. The Curie-Weiss like χ was found for La x , and the absolute value of the antiferromagnetic Weiss temperature increases with x until 0.3 and then decreases. For La 0.3 the Curie-type χ appeared overlapping the Curie-Weiss χ below 50 K, and there was no clear peak in χ down to 5 K. The resistance anomaly may have been caused either by the Kondo scattering, or a localization effect and/or an electron-electron interaction under the random distribution of hetero-valent cations.
TL;DR: In this paper, the S-shaped temperature dependence of the mixed-valent x = 0.0 alloy is not a single-ion property; the most interesting observation is that, for an intermediate concentration, ( x =0.25), a linear temperature dependence is found below 30 K, an observation of relevance to the current trends in the topic of non-Fermi-liquid behavior.
TL;DR: The theoretical phase diagrams of a magnetic lattice fluid in an external magnetic field are presented in this article, where it is shown that, depending on the strength of the nonmagnetic interaction between particles, various effects of the external field on the Ising fluid take place.
Abstract: The theoretical phase diagrams of a magnetic (Ising) lattice fluid in an external magnetic field are presented. It is shown that, depending on the strength of the nonmagnetic interaction between particles, various effects of the external field on the Ising fluid take place. In particular, at moderate values of the nonmagnetic attraction the field effect on the gas-liquid critical temperature is nonmonotonic. A justification of such behavior is given. If short-range correlations are taken into account (within a cluster approach), the Curie temperature also depends on the nonmagnetic interaction strength.
TL;DR: In this paper, two new compounds Pr3Co13B2 and Nd5Co19B6 have been synthesized successfully, which belong to the Rm+nCo5m+3nB2n family.
Abstract: New compounds Pr3Co13B2 and Nd5Co19B6 have been synthesized successfully. They belong to the Rm+nCo5m+3nB2n family with m = 2, n = 1 and m = 2 and n = 3, respectively. Pr3Co13B2 adopts the hexagonal La3Ni13B2-type structure with lattice parameters a = 5.0672(3) Angstrom and c = 10.6850(6) Angstrom, while Nd5Co19B6 is isostructural to Lu5Ni19B6 With a = 5.1328(3) Angstrom and c = 16.6519(5) Angstrom. Magnetic measurements indicate that Pr3Co13B2 is ferromagnetic with a Curie temperature of 360 K. Its saturation magnetic moment at 5 K is 20.0 mu(B) fu(-1). Based on the results of the saturation magnetization, two kinds of Co sites with different magnetic moments are proposed. Pr3Co13B2 exhibits large uniaxial anisotropy with an anisotropy field of 90 A m(-1) at 5 K. The Nd5Co19B6 compound is ferromagnetic with a Curie temperature of 380 K. Its saturation magnetic moment and anisotropy field are 21.5 mu(B) fu(-1) and 340 A m(-1) at 5 K, respectively. No spin reorientation was detected from the temperature dependence of the magnetization of these compounds from 5 K to their Curie temperatures, and the behaviour of magnetocrystalline anisotropy was analysed using the single-ion model.
TL;DR: Magnetic properties of palladium sulfide bronzes RPd3S4 (R=Ce, Gd) are reported in this paper, where the initial magnetization and magnetic hysteresis loop were measured at 2 K by changing the applied magnetic field between −5 and 5 T.
TL;DR: In this paper, structural, electric and magnetic measurements have been performed on the new rare earth intermetallic compound Gd 2 Ni 2 Cd, which crystallises in the Mn 2 B 2 Al-type structure and undergoes an antiferromagnetic transition at 65 K.
TL;DR: In this article, a new compound with chemical formula YbZn 2 As 2 and anti-La 2 O 3 -type crystal structure (space group P 3 m 1) has been synthesized for the first time.
TL;DR: In this article, the results of a search for superconductivity in Li were reported, and no evidence for the predicted transition to superconductability at any temperature down to 5 mK in magnetic fields down to 0.4 uT.
Abstract: We report on the results of a search for superconductivity in Li. We find no evidence for the predicted transition to superconducti vity at any temperature down to 5 mK in magnetic fields down to 0.4 uT. However, an unexpected Curie- Weiss temperature dependence in the magnetic susceptibility is observed. We discuss the possibility that this signal arises from the Li itself, the possibility that it arises from Kondo behavior, and the implications of the effect for the predicted Tc of Li.