Curie-Weiss Relation Research Articles

Kondo behaviour of Ce 1− xLa xCu 5In and CeCu 5In 1− xM x (M=Al or Ga)

Electrical resistivity ρ( T) measurements for compounds of the Ce 1− x La x Cu 5In and CeCu 5In 1− x M x (M=Al or Ga) series indicate the evolution from coherent Kondo to incoherent Kondo behaviour as x is increased. The magnetic susceptibility of the compounds follows a Curie–Weiss relation.

Permittivity and Microstructure of (Ba,Sr)TiO3 Films: Temperature and Electric Field Response

AbstractEpitaxial heterostructures (001)(Y,Nd)Ba2Cu3O7-δ∥(100)SrTiO3∥(001)(Nd,Y)Ba2Cu3O7-δ,(100)SrRuO3∥(100)Ba0.8Sr0.2TiO3∥(100)SrRuO3, (100)SrRuO3∥(100)SrTiO3∥(100)SrRuO3 and (100)SrTiO3∥(001)YBa2Cu3O7-δ have been grown by laser ablation. There was only a small difference of the dielectric permittivity, in the temperature range 180-300K, between a bulk single crystal and an epitaxial (100)SrTiO3 layer inserted between either high-Tc superconducting or SrRuO3 electrodes. At T<1 50K, on the other hand, the response of the dielectric permittivity of the SrTiO3 layer on temperature or electric field depended to a large extent upon the materials used as bottom and top electrodes in the heterostructures. The temperature dependence of the dielectric permittivity for the SrTiO3 layer in (100)SrRuO3∥(100)SrTiO3∥(100)SrRuO3 was well extrapolated by a Curie-Weiss relation in the range of T=80-300K, with about the same Curie constant (C0=7.5 × 104 K) and Curie temperature (TCurie=21K) as in a bulk single crystal. At temperatures higher the phase transition point (65 K), the electric field response of the permittivity of the SrTiO3 layer between high-TC superconducting or metallic oxide electrodes was well extrapolated by the same relation used for a bulk single crystal. The smallest loss factor, tanδ, was measured for the capacitance (100)SrRuO3∥(100)SrTiO3∥(100)SrRuO3 (T ≈ 50-300K, f=100kHz). The measured conductance G for the SrTiO3 layer in the (001)(Y,Nd)Ba2Cu3O7-δ heterostructure fitted well the relation InG∼-(ED/kT), with ED=0.08-0.09 eV in a temperature range close to 300K. Pronounced hysteresis was observed in the temperature dependence of the dielectric permittivity for the (100)Ba0.8Sr0.2TiO3 layer at temperatures close to the phase transition point, like in the case of a bulk single crystal. The permittivity of the (100)Ba0.8Sr0.2TiO3 layer decreased more than 50% when an electric field of 2.5×106V/m (T ≈ 300K, f=100 kHz ) was applied.

Anomalous behavior of dielectric permittivity of Li2Ge7O15 crystals at a phase transition

It is shown that the Curie-Weiss relation describes unsatisfactorily the temperature dependence of dielectric permittivity at the transition from orthorhombic paraphase to polar phase.

Superconductivity and normal-state magnetism of CaLaBaCu 3− xCo xO 7 superconductor

The results of superconductivity and normal-state magnetism of the CaLaBaCu 3 − x Co x O 7 superconductor for x = 0.0–0.24 are studied by X-ray diffraction and SQUID magnetization. The transition temperature T c of the samples, determined from AC susceptibility measurements decreases with an increase in the dopant Co concentration. The normal-state high-field (5 kOe) DC magnetism inferred that the pure sample ( x = 0.0) has a small and nearly temperature-independent molar susceptibility, while the Co-doped samples follows the Curie-Weiss relation in terms of the paramagnetic moment on the dopant Co.

Magnetic properties of the crystals of p-(1-oxyl-3-oxido-4,4,5,5-tetramethyl-2-imidazolin-2-yl)benzoic acid and its alkali metal salts

The crystals of p-(1-oxyl-3-oxido-4,4,5,5-tetramethyl-2-imidazolin-2-yl)benzoic acid and its alkali metal (Li, Na, and K) salts were prepared. Dimer structures were found in the crystals of the free acid 1 and the lithium salt 1·Li· 1 2 MeOH by X-ray crystal structure studies. A dimer model was fitted to the observed magnetic susceptibility data of 1 and 1·Li· 1 2 MeOH in the whole temperature range studied. The optimized exchange coupling parameters 2 J/ k B in the dimers were −6.0 and +31.8 K in 1 and 1·Li· 1 2 MeOH, respectively. The sodium and potassium salts were paramagnetic and analyzed in terms of the Curie-Weiss relation to have weak Weiss fields of θ = −0.4 and −1.0 K, respectively.

Magnetic behaviour of CuIn1-zFezS2

Single-phase polycrystalline samples of CuIn1-zFezS2 (0.04<z<0.6) alloys with a chalcopyrite structure were studied by measurement of the low-field magnetic susceptibility chi and ESR in the temperature range 4-300 K, and by room-temperature Mossbauer spectroscopy. At the higher temperatures, the 1/ chi versus T data could be interpreted in terms of a modified Curie-Weiss relation, and values of the Curie-Weiss temperature (-) and Curie constant C were obtained. At lower temperatures, the 1/ chi versus T curves for each sample with z>0.2 showed a minimum corresponding to a magnetic transition temperature Tc and the overall behaviour of the alloy system seems similar to the spin-glass form displayed by various semimagnetic semiconductor alloys containing Mn. The chi data show that, in the present system, the average magnetic moment of the Fe changes rather abruptly from a value corresponding to S=5/2 for z < 0.05 to S=3/2 for z>0.2. However, the Mossbauer spectra indicate that the Fe remains in the Fe3+ state throughout the full composition range studied. The change in the magnetic moment is attributed to a change in the spin configuration of Fe3+, and possible explanations for this are discussed.

Deviation from Curie-Weiss behavior in relaxor ferroelectrics.

The deviation from Cure-Weiss behavior has been investigated in lead magnesium niobate relaxor ferroelectrics. At high temperatures, the susceptibility was found to follow the Curie-Weiss relationship. A Curie constant and temperature of 1.2\ifmmode\times\else\texttimes\fi{}${10}^{5}$ and 398 K, respectively, were obtained. With decreasing temperature the deviation was found to increase. It is proposed that this deviation arises due to short-range correlations between polar regions, and that these correlations at high temperatures are the precursor to a freezing of the polarization fluctuations into a glassy state. A local (glassy) order parameter was calculated from the susceptibility by analogy to spin glasses [D. Sherrington and S. Kirkpatrick, Phys. Rev. Lett. 35, 1972 (1975)]. These results are compared to the rms polarization [G. Burns and F. Dacol, Solid State Commun. 48, 853 (1983)] and to the measured remanent polarization. The frequency and field dependence has also been investigated.

Exchange interaction in rare-earth-doped IV-VI diluted magnetic semiconductors.

The magnetization and magnetic susceptibility of Bridgman-grown ${\mathrm{Sn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Gd}}_{\mathit{x}}$Te samples with values of x up to 0.09 have been measured in fields up to 5.5 T over a temperature range from 2 to 300 K and in fields up to 23 T at 4.2 K. The low-field, high-temperature susceptibility data followed the Curie-Weiss relation with a small Curie temperature. The magnetic-field dependence of the magnetization was fitted to an expression containing a Brillouin function, representing isolated magnetic ions, plus a term representing pair interactions. Both the susceptibility and the high-field magnetization data indicated a weak antiferromagnetic coupling among Gd ions. These results are compared with our previously obtained exchange parameters for ${\mathrm{Pb}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Gd}}_{\mathit{x}}$Te and ${\mathrm{Pb}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Eu}}_{\mathit{x}}$Te. The exchange interaction in ${\mathrm{Sn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Gd}}_{\mathit{x}}$Te is larger than in PbTe-based, rare-earth-doped chalcogenides, in agreement with the smaller cation-anion spacing in SnTe-based compounds. A ferromagnetic or spin-glass ordering due to the possible Ruderman-Kittel-Kasuya-Yosida interaction in ${\mathrm{Sn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Gd}}_{\mathit{x}}$Te with high hole concentration was not observed.

Magnetization and Susceptibility of Sn1-xGdxTe

The magnetization and magnetic susceptibility of Bridgman-grown Sn1-xGdx Te with values of x up to 0.09 have been measured over a temperature range from 2 to 300 K and in magnetic fields up to 5.5 T. The magnetic susceptibility data followed the Curie-Weiss relation with a small Curie temperature that indicated a weak antiferromagnetic coupling among Gd ions. The magnetic field dependence of the magnetization was fitted to a modified Brillouin function with parameter values that agreed fairly well with those from Curie-Weiss plots. The value of the exchange parameter was larger than in Pb1-xG dxTe. The samples were p-type with carrier concentrations up to 1.3 x 10 21 cm'. The ferromagnetic or spin-glass phase due to the RKKY interaction was not observed.

Ferroelectric Activity on Organic Crystal Trichloroacetamide

Dielectric constants and D - E hysteresis loops have been measured on trichloroacetamide (TCAA) single crystals. Only along the crystallographic b -axis are remarkable dielectric anomalies found at T C =354.6 K and T I =356.9 K upon heating. The Curie-Weiss relation holds in the high-temperature phase with a very small Curie constant of about 5.6 K. Typical ferroelectric D - E hysteresis loops are observed only in a limited temperature range of a few degrees just below T C ; the spontaneous polarization P s and the coercive field E c are estimated to be about 0.2 µC/cm 2 and 4 kV/cm, respectively, at 350 K. Since the E c steeply increases with decreasing temperature, it is difficult to reverse the P s at room temperature. Some discussions are presented for the causes of the weak ferroelectricity on TCAA.

Magnetic Susceptibility of Pb1-x-ySnyMnxSe

Magnetic susceptibility has been measured in Pb1x-ySnyMnxSe with x values up to 0.02 and y values up to 0.05. The measurements were carried out using a SQU1D system over a temperature range from 5 to 250 K. The susceptibility followed the Curie—Weiss relation with a small paramagnetic Curie temperature that indicated a weak antiferromagnetic exchange interaction between Mn ions. We analyzed the results together with our previously published data on highfield magnetization in this material. A reasonable agreement of the exchange parameters obtained from the low-field susceptibility and high-field magnetization data was obtained.

Magnetization and susceptibility of Pb 1− xEu xTe

The magnetization and magnetic susceptibility of Bridgman-grown Pb 1− x Eu x Te with values of x up to 0.06 have been measured over a temperature range from 4.2 to 250 K and in magnetic fields up to 23 T. The magnetic field dependence of the magnetization was fitted to an expression containing a Brillouin function, representing isolated magnetic ions, plus a term representing pair interactions. The low-field high-temperature susceptibility data followed the Curie-Weiss relation with a small Curie temperature, that indicated a weak antiferromagnetic coupling among Eu ions. The exchange parameters estimated from the high-field magnetization and the low-field susceptibility were in good agreement.

Magnetization and susceptibility of Pb1−xMnxSe

Susceptibility and magnetization have been measured in samples of Pb 1− x Mn x Se with small values of x over a temperature range from 2 to 300 K. The high temperature susceptibility followed the Curie-Weiss relation with a small paramagnetic Curie temperature that indicated a weak antiferromagnetic coupling among Mn ions. The high field magnetization could be fitted to a modified Brillouin function.

Magnetic characteristics of superconducting RBa 2Cu 3O 6+y ( R = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm and Yb)

Magnetic properties of superconducting RBa 2Cu 3O 6+y compounds ( R = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm and Yb) have been studied by using a SQUID magnetometer in the temperature range of 3 – 400 K. The susceptibility data of most of the samples can be well described by the Curie-Weiss relation. The rare earth ions exhibit essentially the full magnetic moments expected for the R 3+ states, while the superconducting transition temperature remains in the 88 – 94 K range. The rare earth moments are generally found to interact antiferromagnetically. However, no magnetic order is observed in the temperature range studied. The Eu samples exhibited anomalous susceptibilities which we ascribe to the low-lying states of the 7F J manifold of Eu 3+.

Author index to volume 52

Measurements of electrical resistivity ρ(T), magnetoresistivity MR and magnetic susceptibility χ(T) are reported for the pseudo-ternary alloys (Ce1-xYx)Pt2Si2. ρ(T) results reveal coherent Kondo scattering above 80% Ce concentration and a rapid evolution to single-ion Kondo scattering with an increase in Y concentration x. MR measurements on Ce alloys in the single-ion Kondo region are analyzed on the basis of calculations by Schlottmann for the Bethe-ansatz solution in the context of the Coqblin–Schrieffer model. The analysis yields values of the Kondo temperature TK and the effective moment of the Kondo ion μK. χ(T) data above 120 K follow the Curie-Weiss relation for all the investigated concentrations and give effective moment values μeff in close agreement with μeff=2.54μB expected for the Ce3+-ion.

Magnetic and electric hyperfine interactions in the system EuSm

Magnetic and electric hyperfine interactions in the system EuSm were investigated with the isomeric 11/2− state in145Eu by applying the time-differential perturbed angular distribution (TDPAD) method. The temperature dependence of paramagnetism was studied between 90 K and 1000 K by measuring the magnetic hyperfine interaction frequency ωL=gNμNħ1 β(T)Bext. The paramagnetic correction factor β strictly follows the Curie-Weiss relation β=1+C/(T-θ), withC=−50(2) K and θ=−29(5) K. This is compatible with a hyperfine field ofBint(0)=−25(1) T, a valence of two for Eu in Sm, and antiferromagnetic order at low temperatures.

Study of phase transitions and properties of tetragonal (Pb, La) (Zr, Ti)O3 ceramics. Part I: Phase diagram and β-phases

Measurements of electrical resistivity ρ(T), magnetoresistivity MR and magnetic susceptibility χ(T) are reported for the pseudo-ternary alloys (Ce1-xYx)Pt2Si2. ρ(T) results reveal coherent Kondo scattering above 80% Ce concentration and a rapid evolution to single-ion Kondo scattering with an increase in Y concentration x. MR measurements on Ce alloys in the single-ion Kondo region are analyzed on the basis of calculations by Schlottmann for the Bethe-ansatz solution in the context of the Coqblin–Schrieffer model. The analysis yields values of the Kondo temperature TK and the effective moment of the Kondo ion μK. χ(T) data above 120 K follow the Curie-Weiss relation for all the investigated concentrations and give effective moment values μeff in close agreement with μeff=2.54μB expected for the Ce3+-ion.

The structure and magnetic properties of non-crystalline vapour quenched Gd-Ag and Gd-Cu alloys

Abstract A number of Gd-Ag and Gd-Cu non crystalline alloy films containing between 0 and 60 at.% Ag or Cu have been prepared by the vapour quench techniques. The alloys are found to be ferromagnetic with a Curie temperature which falls to 40 K for alloys containing 13 at.% Ag or Cu. The magnetic susceptibility follows a Curie-Weiss relationship with temperature and gives peff = 7.6 ± 1.9 μB.

The tetrafluorides of iridium, rhodium and palladium

The noble-metal tetrafluorides IrF 4, RhF 4 and PdF 4 have been synthesized. All three fluorides are isostructural with PtF 4 the unit cells being face centred orthorhombic, Z = 8, (probable space Fdd2) with the following parameters: a 0( A ̊ ) b 0( A ̊ ) c 0( A ̊ ) V( A ̊ 3) IrF 4 9·64(2) 9·25(2) 5·67(1) 505·8 RhF 4 9·71(2) 9·05(2) 5·63(1) 494·7 PdF 4 9·37(2) 9·24(2) 5·84(1) 505·6 PdF 4 is diamagnetic (low spin d 6) whereas RhF 4 and IrF 4 are paramagnetic. The magnetic susceptibility of the latter obeys a Curie-Weiss law over the temperature range 100–300°K (θ = − 60°K) with μ eff = 1·89 B.M.. Below 100°K significant deviation from the Curie-Weiss relationship occurs. This and the large negative value of the Weiss temperature are consistent with antiferromagnetic coupling between adjacent iridium atoms. This is in harmony with a proposed structural model.

Ferroelasticity of Niobium due to Hydrogen as a Lattice Gas

We have measured the elastic response of niobium in the region of the critical point of hydrogen in niobium. The elastic susceptibility exceeds commonly observed values by two or three orders of magnitude and follows a Curie-Weiss relation over the temperature range investigated. The diffusion coefficient of hydrogen shows "critical slowing down" behavior but no anomaly in the transport coefficient.