Showing papers on "Curie–Weiss law published in 1997"
TL;DR: In this article, a temperature-sensitive magnetic fluid with a low Curie temperature is synthesized, characterized by x-ray diffraction, magnetization, and small angle neutron scattering (SANS).
Abstract: A temperature-sensitive magnetic fluid with a low Curie temperature is synthesized. The fluid is characterized by x-ray diffraction, magnetization, and small angle neutron scattering (SANS). Low Curie temperature of the fluid enables us to separate out the nuclear and magnetic scattering contributions in SANS by recording the SANS pattern at two temperatures.
88 citations
TL;DR: In this paper, the magnetic properties of the system were studied in which an intermediate-valence state of Eu is realized at around x = 0.75, and it was found that the compounds with show a temperature-induced valence transition below room temperature, while those with are antiferromagnetic with a stable state.
Abstract: The magnetic properties of the system were studied in which an intermediate-valence state of Eu is realized at around x = 0.75. It was found that the compounds with show a temperature-induced valence transition below room temperature, while those with are antiferromagnetic with a stable state. A first-order valence transition induced by high magnetic field was observed for . Such valence transitions against temperature or field are discussed on the basis of the interconfigurational fluctuation (ICF) model. It is shown that the observed linear relation between the transition field and the transition temperature is explained by the present model.
70 citations
TL;DR: In this article, the magnetic properties of orthorhombic LiMnO 2 have been investigated in detail for the first time, and the magnetic structure has been solved from neutron diffraction data and has a propagation vector of k =(1/2 1/2 2 1 2 ) and an ordered magnetic moment of 3.69(4) μ B /Mn 3+ with a preferred direction parallel to the b axis.
68 citations
TL;DR: In this paper, the Curie temperature of a ferroelectric ceramics with 1.0 mol.% MgO and 0.05 mol. MnO 2 was prepared with a rate-controlled sintering profile and the lattice constant of this BST system decreases as the strontium molar fraction increases.
63 citations
TL;DR: In this paper, dielectric measurements were performed for ceramics from to Hz in the temperature range 85 - 700 K. The temperature and frequency dependence of the permittivity was fitted by the Curie-Weiss law beyond the transition temperature and characterized by parameters that are used to describe relaxor behaviour.
Abstract: ceramics with x = 0.1, 0.2, 0.3, 0.33, 0.4 and 0.5 have been synthesized by the mixed oxide method. Dielectric measurements were performed for ceramics from to Hz in the temperature range 85 - 700 K. The dielectric measurements confirmed that the solid solution range extends up to about x = 0.3. In the solid solutions, the temperature of the permittivity maximum was shifted at a rate of -7 K/mol% Ce atom and the permittivity maximum decreased with increasing Ce content. The temperature and frequency dependence of the permittivity was fitted by the Curie - Weiss law beyond the transition temperature and characterized by parameters that are used to describe relaxor behaviour.
49 citations
TL;DR: The magnetic properties of the ten title compounds were investigated with a SQUID magnetometer in the temperature range of 2-400 K with magnetic flux densities up to 5.5 T as mentioned in this paper.
42 citations
42 citations
TL;DR: In this paper, the crystal structure of the ordered perovskites Ba{sub 2}(RSb)O{sub 6} (R = Y, Ho) is refined from neutron powder diffraction data in the space group Fm3m (No. 225), Z = 4, with Ba at 8(c), R at 4(b), Sb at 4 (a), oxygen at 24(e), oxygen positional parameter x = 0.4240(3) and 8.4170(2) for R = Y and Ho, respectively.
40 citations
TL;DR: In this paper, the Curie-Weiss paramagnetic temperatures obtained from the low-temperature region depend linearly on the concentration x, and its calculation requires inclusion of the first excited Kramer's doublet.
Abstract: Polycrystalline samples of the new semimagnetic semiconductor (x = 0.06, 0.12, 0.25, 0.39, 1.00, 1.40, 1.80) were obtained by ceramic technology. An x-ray diffraction experiment was performed on all of the samples at room temperature. These data provided the basis for Rietveld refinements. The refinements showed that ions preferentially occupy the 24d position. The lattice constants and the mean cation - anion distances decrease linearly with the -ion concentration. The inverse magnetic susceptibilities for all of the samples depend linearly on the temperature for . In this region only the lowest Kramer's doublet is populated, and for that level the effective magnetic quantum number is deduced. The Curie - Weiss paramagnetic temperatures obtained from the low-temperature region depend linearly on the concentration x. Over the whole experimental region , the magnetic susceptibility deviates from the Curie - Weiss law, and its calculation requires inclusion of the first excited Kramer's doublet. The effective magnetic quantum number and energy gap of the first excited doublet were deduced.
40 citations
TL;DR: In this article, different grain sizes of ferroelectric Ba0.65Sr0.35TiO3 doped with 1.0 mol% MgO and 0.05 mol% MnO2 were investigated to investigate the DC field dependence of dielectric characteristics.
Abstract: Different grain sizes of ferroelectric Ba0.65Sr0.35TiO3 doped with 1.0 mol% MgO and 0.05 mol% MnO2 were prepared to investigate the DC field dependence of dielectric characteristics. A transition broadening is observed as grain size decreases. The broadening is attributed to the variance of lattice distortion in the materials. As the grain size increases, both the maximum dielectric constant k max at T c and the dielectric tunability (percentage change of dielectric constant under a DC field) increase. A phenomenological equation can be fit to the DC field dependence of the dielectric constant. The phenomenological coefficient obtained is strongly dependent on the grain size and the temperature. Above the phase transition, a "behavior-transformation" temperature T b is observed. At temperatures below T b, the dielectric loss factor that is dominated by intrinsic loss is reduced when the DC field is applied. While at temperatures above T b, the loss factor is dominated by the conduction loss and is raised by the DC field.
38 citations
TL;DR: In this article, bulk magnetic properties of selected Re70M30−xTx (with Re = Gd, Dy, Er, Ho, Tb and M, T = Ni, Fe, Cu, Al) alloys have been investigated in the 5-350 K temperature and 0-7 T DC field range.
TL;DR: In this paper, a magnetic entropy change larger than that of gadolinium was observed in perovskite manganites La 0.67−x Gd x Ca 0.33 MnO 3 (x = 0, 0.05,0.1, and 0.15) with fixed carrier concentration.
TL;DR: The magnetic behavior of then=2 Ruddlesden-Popper compounds has been investigated in this paper, showing that the magnetic response is sensitive to changes in the relative strength of superexchange and double exchange interactions as a function of the lanthanide cation.
Abstract: The magnetic behaviour of then=2 Ruddlesden–Popper
phases Sr
2
LnMn
2
O
7
is very sensitive to
the Ln
3+
lanthanide cation. In samples with larger, more basic
lanthanide cations (Ln=Nd, Pr) antiferromagnetic phases with ordering
temperatures in the region of 130 K co-exist with phases showing a
magnetic response suggestive of superparamagnetism or the development of
small ferromagnetic clusters at high temperature. The magnetic transition
temperature drops to 20 K in samples containing smaller, acidic cations
(Ln=Gd–Er, Y). In the latter group of compounds, the transition is
from a Curie–Weiss paramagnet to a spin-glass; there is no evidence
for long-range magnetic order. This change in behaviour can be explained
by considering the variation in the relative strength of superexchange and
double exchange interactions as a function of the lanthanide cation. The
influence of manganese oxidation state on magnetic response is
investigated in the Sr
2-x
Ln
1+x
Mn
2
O
7
composition range
(0.0≤x≤0.7) for Ln=Nd, Tb.
TL;DR: In this paper, the temperature dependence of the magnetic susceptibility of FeSi is calculated over a wide temperature range on the basis of spin-fluctuation theory applied to a model of an exchange-enhanced semiconductor.
Abstract: The temperature dependence of the magnetic susceptibility of FeSi is calculated over a wide temperature range on the basis of spin-fluctuation theory applied to a model of an exchange-enhanced semiconductor. We can reproduce the low-temperature activation-type behaviour of the susceptibility as well as the Curie - Weiss behaviour observed at high temperature. We also give an explanation for the behaviour of the observed wave-vector- and frequency-dependent neutron scattering intensities.
TL;DR: In this paper, Maghemite with spontaneous saturation magnetization M s = 320 kA m −1 at 200 K and a normalized high-field susceptibility χ /M o = 5.1 × 10 −6 m kA −1, practically independent of temperature.
TL;DR: In this article, the specific magnetization σ(T,B ), torque moments L ( ϕ ), Young's modulus E(T), internal friction Q −1 (T), and magnetostriction λ( B ) of a single crystal and polycrystalline samples, of the SmFe 11 Ti compound, in the temperature region 77-700 K in magnetic fields up to 1.6 T.
TL;DR: In this article, the physical properties of Dy(Co 1− x Al x ) 2 cubic compounds were investigated and the composition dependence of the Curie temperature was discussed on the basis of electronic structure calculations.
TL;DR: In this article, the magnetization of F and P-type icosahedral Al - Pd - Mn was studied in the temperature region between 2 and 870 K in a magnetic field below 80 kOe.
Abstract: The magnetization of F- and P-type icosahedral Al - Pd - Mn was studied in the temperature region between 2 and 870 K in a magnetic field below 80 kOe. F-type icosahedral phase samples obtained by quenching from 1075 K were transformed to the low-temperature-phase form during the magnetic measurement above 600 K. The low-temperature phase is a P-type phase; this phase is characterized by a superlattice ordering. The samples showed Curie - Weiss paramagnetism and increasing susceptibility with increasing temperature at high temperatures. The increasing susceptibility is accounted for by a temperature dependence of the Pauli paramagnetism arising from a pseudogap at in the electronic density of states. The increase in the P phase was larger than that in the F phase, which indicates an enhanced pseudogap in the P phase. This is consistent with a structural transformation to a more stable P phase caused by the in situ heat treatment. The Curie - Weiss susceptibility decreased after the structural transformation from F- to P-type structure had occurred. A reduction by about one half in the number of magnetic Mn atoms in the transformation is inferred. The temperature dependence of the susceptibility deviates from the Curie - Weiss law below 30 K, which is similar to what was found in a previous report by Chernikov and co-workers, but the deviation is much smaller.
TL;DR: In this article, a double-layered perovskite material with a tetragonal unit cell with a = 3.9221(3) A and c = 7.6648(8) A was synthesized.
Abstract: We report on the synthesis of YBaMn 2 O 5+δ , a new double-layered perovskite material having a tetragonal unit cell with a = 3.9221(3) A and c = 7.6648(8) A. Magnetic susceptibility measurements show X mol = (8.9±0.1 x 10 -3 ) emu mol -1 at 300 K which obeyed a Curie-Weiss law (θ = -43 ± 1 K) down to 166 K ( T N ) where a large magnetic transition occurs. Above T N , a temperature independent μ eff = (4.19 ± 0.07) μ B was observed; this is attributed to arising from a magnetic lattice with mixed oxidation state with the main ion being high spin Mn III (d 4 ) with S = 2.
TL;DR: In this article, the magnetic properties of Tb 2 Co 17− x Ga x compounds (x = 1,3,5 and 7) were studied by means of neutron diffraction and magnetic measurements.
TL;DR: In this article, a magnetic study of perovskites R(Mn 1−xBx)O3 (R Eu, Gd, Tb, Dy, Y; B Ni, Co) is reported.
TL;DR: In this article, the formation of metastable dipolar gratings in potassium lithium tantalate niobate at the paraelectric phase was shown to result from local metastable changes in the Curie-Weiss temperature.
Abstract: We present experimental evidence indicating the formation of metastable dipolar gratings in potassium lithium tantalate niobate at the paraelectric phase. These dipolar gratings result from the formation of local metastable changes in the Curie-Weiss temperature, which, in the presence of an external electric field, induce changes in the low-frequency polarization. The polarization changes create spatially correlated birefringence gratings due to the electro-optic effect. The dipolar gratings are formed in a slow spontaneous process, to compensate for regular photorefractive gratings immediately after the creation of the latter.
TL;DR: NbFeTe2 is a layered cluster compound in which intra Fe-Fe bond distance is 2.488 A. The magnetic susceptibilities between 100 and 300 K are fit to Curie-Weiss law with C=1.29 emu K/mol, and θ=+69.2 K as discussed by the authors.
Abstract: NbFeTe2 is a layered cluster compound in which intra Fe–Fe bond distance is 2.488 A. The magnetic susceptibilities between 100 and 300 K are fit to Curie–Weiss law with C=1.29 emu K/mol, and θ=+69.2 K. The effective magnetic moment of 3.67 μB per Fe at 300 K corresponding to three unpaired electrons may suggest the formation of Fe–Fe single bond. Mossbauer spectrum at 77 K shows a paramagnetic doublet with δ=0.36 mm/s and ΔE=0.62 mm/s. The χac measurement reveals the occurrence of a spin glass transition at Tf=44.0 K. The irreversibility of magnetic properties below Tf has been studied with the measurements of the dc susceptibility, remanent magnetization, and hysteresis loop for both zero field cooled and field cooled samples. The competition between antiferromagnetic and ferromagnetic interactions probably cause the spin glass behavior.
TL;DR: In this article, the structural and magnetic changes that take place after the lithium exchange reactions of MnXO4·D2O to give LiMn XO4(OD) (X=P, As) have been studied by magnetic susceptibility and variable-temperature neutron diffraction techniques.
TL;DR: In this article, the electronic structure of Fe3B in orthorhombic (o-Fe3B) and body-centered tetragonal (bct-Fe 3B) structures was calculated using the spin-polarized linear muffin-tin orbitals method.
Abstract: The electronic structure of Fe3B in orthorhombic (o-Fe3B) and body-centered tetragonal (bct-Fe3B) structures are calculated using the spin-polarized linear muffin-tin orbitals method. Based upon the calculated electronic structure, we present theoretical results on the cohesive energy (E-coh) local magnetic moment (mu(loc)), and hyperfine magnetic field (H-hf) for the two phases of Fe3B. Effects of the neighboring atoms on mu(loc) and E-coh at individual Fe sites have been discussed in detail. Within the framework of the spin fluctuation of local moments we have evaluated the ratio of the Curie temperature T-C for o- and bct-Fe3B, and also investigated the volume dependence of T-C. Some numerical results are given and the theoretical results agree qualitatively with the experimental results.
TL;DR: The effect of pressure on the Curie temperature and saturation magnetization σ at 42 K for Co2B was investigated in this paper, where it was shown that Tc decreases linearly with pressure.
TL;DR: In this paper, the pseudocubic lattice parameter of 3.916 A is larger than that of the undoped LaMnO3 material, consistent with substitution at the Mn site.
Abstract: Crystalline powders of Na-doped LaMnO3 have been precipitated from molten sodium hydroxide at 450 °C. Elemental analysis by wavelength dispersive spectroscopy indicates than Na substitutes for Mn giving LaMn1−xNaxO3+δ, with x=0.2. The pseudocubic lattice parameter of 3.916 A is larger than that of the undoped material, consistent with substitution at the Mn site. Analysis of magnetic susceptibility gives a ferromagnetic Curie–Weiss temperature of 130 K, which is to be compared with the onset of weak ferromagnetism near 300 K. Low-temperature magnetization measurements suggest a model of canted antiferromagnetic clusters.