Showing papers on "Curie–Weiss law published in 1988"
TL;DR: In this article, the compositional variation of saturization magnetization and Curie temperature for Ni1−y−xZnxCuyFe2O4 where x = 0.0, 0.6, 0., 0.8, 1.0 for y = 0 and x =0.2 have been reported.
84 citations
75 citations
TL;DR: In this paper, the Inoue-Shimizu model was used to analyze the induced character of the cobalt magnetic moment in ErxY1-xCo2 compounds.
Abstract: Ferromagnetic compounds of the series ErxY1-xCo2 (x=1, 08, 07, 06) have been investigated in specific-heat, thermal-expansion, magnetisation, AC susceptibility and resistivity experiments The magnetic moment on the Co atoms decreases with decreasing Er content, as does the Curie temperature The character of the magnetic transition changes from first order to second order around x=07 This change is compared with the similar one observed in other RExY1-xCO2 compounds with RE-Gd, Tb, Dy and is discussed in terms of the Inoue-Shimizu model by taking into account the strong temperature dependence of the magnetic susceptibility of the 3d electrons The spontaneous volume magnetostriction at zero temperature, the magnetic contribution to the specific heat and the magnetic entropy below the magnetic ordering temperature are determined The experimental results for these quantities confirm the induced character of the cobalt magnetic moment in these compounds
52 citations
TL;DR: The effect of substitution of Y atoms for Ca atoms has been studied in the Bi 2 Sr 2 Ca 1- x Y x Cu 2 O y compound system as discussed by the authors, showing that the electrical resistivity behavior can be well described by the three-dimensional variable range hopping conduction, indicating that the system is essentially insulating.
Abstract: The effect of substitution of Y atoms for Ca atoms has been studied in the Bi 2 Sr 2 Ca 1- x Y x Cu 2 O y compound system. For x x , though the transition temperature of about 85 K is maintained. For x ≧0.5 samples, the electrical resistivity behavior can be well described by the three-dimensional variable range hopping conduction, indicating that the system is essentially insulating. In this range of x , magnetic susceptibility shows spin-glass-type cusp at 13 K in the heating process after zero-field cooling and an enhanced cusp at 11 K in the field-cooling process. In the temperature range above about 150 K the Curie-Weiss dependence holds well with a positive paramagnetic Curie temperature, which increases to 40 K with increasing x in the insulating region.
52 citations
TL;DR: In this article, the authors measured the low-temperature specific heat and dc magnetic susceptibility of eight samples of the high-Tc superconductor YxBa3−xCu3O7−δ (x=0.9, 1.0, 1 1.1) and two samples of nonsuperconducting YBa2cu3O6+δ.
Abstract: We have measured the low-temperature specific heat (1.3≤T≤20 K) and the dc magnetic susceptibility (100≤T≤250 K) of eight samples of the high-Tcsuperconductor YxBa3−xCu3O7−δ (x=0.9, 1.0, 1.1) and of two samples of nonsuperconducting YBa2Cu3O6+δ. We have also performed specific heat measurements on the possible impurity phases: YBa3Cu2O7, Y2BaCuO5, CuO, and BaCuO2+x. The superconducting samples all have a nonzero, sample-dependent linear term γ* and an upturn inC/T at very low temperature. We show that this anomalous behavior is at least partly due to the presence of a small amount (≈1%) of BaCuO2+x impurity phase in the measured samples. This is evidenced by the correlation between γ* and the Curie component of the susceptibility, which is proportional to the amount of paramagnetic impurities.
41 citations
TL;DR: The Curie-Weiss law of dielectric susceptibility χ in ferroelectrics is derived from two different mechanisms in the self-consistent phonon approximation as discussed by the authors.
Abstract: The Curie-Weiss law of the dielectric susceptibility χ in ferroelectrics is shown to be derived from two different mechanisms in the self-consistent phonon approximation: One is the increase in the correlation between dipoles which is related to the magnitude of the electrostatic interaction D . The other is the decrease in the mean square amplitude of the soft mode, which leads to the Curie-Weiss law through the rate of increase 1/ t 0 of an individual susceptibility with the decreasing effective “dipole moment”. The dependence of χ on temperature has been numerically computed to investigate the dependence of the Curie constant on t 0 and D . The ratios of the paraelectric moment to the saturation moment have been evaluated from available experimental data in ferroelectrics. Deviations of these ratios from unity in displacive type ferroelectrics are explained in terms of t 0 .
37 citations
TL;DR: In this paper, the main part of the perpendicular magnetic anisotropy can be considered due to the large one ion magnetization of rare earths, and the dependence of perpendicular magnetic aisotropy on temperature and composition is discussed based on one ion magnetic an isotropy of rare Earth ions.
34 citations
TL;DR: The results of magnetic and X-ray studies have led to a conclusion that the high-temperature ϵ phase of MnGe system, which has D019 type of structure, has the homogeneity range 22.7-24.0 at.% Ge at 800°C and is metastable below ∼515°C as discussed by the authors.
Abstract: The results of magnetic and X-ray studies have led to a conclusion that the high-temperature ϵ phase of MnGe system, which has D019 type of structure, has the homogeneity range 22.7–24.0 at.% Ge at 800°C and is metastable below ∼515°C. The Curie temperature, asymptotic Curie temperature, the Curie constant and the effective magnetic moment per Mn of the weak ferromagnetism, which is parasitic on a triangular antiferromagnetism, are 365 K, -853 K, 2.39 × 10−2 K cm3/g and 3.89 μB, respectively, for 23.5 at.% Ge. The study on a single crystal with 23.0 at.% Ge confirmed that the spontaneous magnetization lies within the basal plane, with zero-field magnetic moment of 0.007 μB/Mn and nearly isotropic incremental susceptibility of 2.0 × 10−5cm3/g, in substantial agreement with the theory by Nagamiya et al.
33 citations
TL;DR: In this paper, the interplay between magnetic properties and chemical ordering in the Co1-xPtx system is investigated theoretically and experimentally Experimental results for the Curie temperature, magnetisation and paramagnetic susceptibility in ordered and disordered states are discussed within the framework of statistical models.
Abstract: The interplay between magnetic properties and chemical ordering in the Co1-xPtx system is investigated theoretically and experimentally Experimental results for the Curie temperature, magnetisation and paramagnetic susceptibility in ordered and disordered states are discussed within the framework of statistical models The authors show that the magnetic moments on Pt atoms depend sensitively on the local chemical environment A complete equilibrium phase diagram is also calculated and compared with the experimental data
28 citations
TL;DR: Magnetic susceptibility measurements on single-crystal specimens of Pr2NiO4+δ and Nd2NO3 and NiO3 were reported in this article, where only minor deviations from the Curie-Weiss law were observed for severely nonstoichiometric samples.
24 citations
TL;DR: In this paper, the temperature dependence of the magnetic flux density at the 151Eu nuclei was determined and compared with theoretical values, where the exchange field acting on the europium ions may be assumed to follow the Brillouin function.
Abstract: Magnetic susceptibility measurements of Eu2Co12P7 show a ferromagnetic phase transition at the Curie temperature of TC=151+or-0.5 K, which is attributed to the magnetic order of the cobalt sublattice. 151Eu Mossbauer spectra reveal an unusual magnetic hyperfine structure splitting of the Van Vleck ion Eu3+. The temperature dependence of the magnetic flux density at the 151Eu nuclei was determined and compared with theoretical values. The exchange field acting on the europium ions may be assumed to follow the Brillouin function, where the best agreement is achieved for J=1. An exchange constant of mu BBexch(0)/k=7.5+or-0.1 K was deduced from the saturation value of the magnetic flux density Bsat=19.0+or-0.1 T. The possible contributions of Fermi contact terms of the magnetic flux density are discussed.
TL;DR: In this paper, the initial susceptibility of a number of Fe3 O4 particle ferrofluids with volume concentrations, e=0.08, 0.07, 0., 0.05 and 0.02 have been measured in the temperature range 220-450 K. The mean particle sizes Dm (magnetic) and Dp (physical) are 74 and 81 A, respectively.
Abstract: The initial susceptibility of a number of Fe3 O4 particle ferrofluids with volume concentrations, e=0.08, 0.07, 0.05, 0.03, 0.02, and 0.01 (prepared by diluting a stock fluid of Ms =40 kA m−1) has been measured in the temperature range 220–450 K. The mean particle sizes Dm (magnetic) and Dp (physical) are 74 and 81 A, respectively. The ferrofluids exhibit Curie–Weiss‐type behavior with negative (Neel) temperature temperature intercepts To . The form of the Curie–Weiss behavior is interpreted as arising from particle interactions which are strong enough to reduce the initial susceptibility below the noninteracting value in the temperature range of measurements. It is suggested that interactions lead to the formation of closed particle structures of zero moment in zero field and, as would be the case for an antiferromagnetic material, leads to Curie–Weiss behavior with a negative ‘‘Neel’’ temperature. Negative values of To are thus characteristic of an interacting particle system.
TL;DR: In this article, the average local moment and the paramagnetic Curie temperature of Al-Mn quasicrystalline and amorphous alloys were determined from the temrerature dependence of susceptibility.
Abstract: Magnetic susceptibility and high field magnetization up to 300 kOe are measured on Al–Mn quasicrystalline and amorphous alloys. The average local moment per Mn, , and the paramagnetic Curie temperature, θ p , are determined from the temrerature dependence of susceptibility. The magnitude of saturation magnetization per Mn, M s , is much smaller than that of , suggesting Mn sites are partly magnetic. The atomic fraction X m . and the average local moment, P c , of the magnetic Mn are estimated from the values of M s and the Curie constant. All the values of X m , P c and |θ p | increase monotonically with increasing Mn content in the quasicrystalline and amorphous phases. The magnetic properties of the quasicrystals are similar to those of the amorphous alloys, but slight differences are observed in the high field magnetization process and the values of X m , P c and θ c .
TL;DR: In this paper, the nuclear magnetization of solid /sup 3/He has been studied by static magnetization measurements from 10 mL down to 03 mK for molar volumes ranging from V = 2414 to 2102 cm/sup 3//mole in the bcc phase and from V= 1983 to 1926 cm/Sup 3/moles in the hcp phase.
Abstract: Nuclear magnetization of solid /sup 3/He has been studied by static magnetization measurements from 10 mL down to 03 mK for molar volumes ranging from V = 2414 to 2102 cm/sup 3//mole in the bcc phase and from V = 1983 to 1926 cm/sup 3//mole in the hcp phase In the bcc phase, both the antiferromagnetic transition temperature T/sub N/ and the reciprocal of the maximum magnetization V/sub max//sup /minus/1/ at T/sub N/ vary in proportion to V/sup 165 +- 1/, and the magnetization below T/sub N/ is constant The magnetization reduced by M/sub max/ is found to represented by a universal function of the reduced temperature T/T/sub N/ In the hcp phase, the magnetization can approximately be represented by Curie's law, and the estimated Weiss temperatures are below 50 muK The authors also observed that the boundary magnetism of liquid /sup 3/He depends considerably on pressure The transition temperature of solid /sup 3/He to the antiferromagnetic phase coexisting with liquid in a restricted geometry is 15% higher than that of the bulk solid on the melting curve
TL;DR: The bulk magnetic properties of tetragonal, oxygen-depleted, polycrystalline samples of sintered R/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/..sqrt../sub x/ compounds with x = 0.95 have been investigated.
Abstract: The bulk magnetic properties of tetragonal, oxygen-depleted, polycrystalline samples of sintered R/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/..sqrt../sub x/ compounds with x = 0.95 have been investigated. Materials containing the rare-earth (RE) ions Gd, Dy, and Ho were studied. In each case, the magnetic susceptibility chi was described by a Curie-Weiss (CW) dependence with effective moments that were very nearly equal to the free-ion values--behavior that is very similar to the superconducting counterparts of these materials where the oxygen has not been depleted. The field dependence of the magnetization M(H,T) was found to be substantially modified by crystalline electric field effects and by the influence of Re-Re interactions.
TL;DR: In this article, the magnetic properties of YBa2(Cu1-xFex)3O7-δ with 0x0.085 were investigated by dc-and ac-magnetic susceptibility in a temperature range from 4.2 to 300 K.
Abstract: Magnetic properties of YBa2(Cu1-xFex)3O7-δ with 0x0.085 were investigated by dc- and ac-magnetic susceptibility in a temperature range from 4.2 to 300 K. The susceptibility in the normal state follows the Curie-Weiss law χ=C/(T-\varTheta)+χ0 with constant paramagnetism χ0. The effective magnetic moments estimated from the Curie constant are 3.4~4.0 µB/Fe, which are consistent with the magnetic moment obtained in the Mossbauer experiments. From the ac susceptibility in the superconducting state, a decrease of volume fraction of superconductivity was observed with increasing Fe-concentration.
TL;DR: In this paper, the temperature dependence of magnetic susceptibility for superconducting Nd1.5Ba 1.5Cu3Oy (Tc~6 K) was measured and the susceptibility of the normal state follows the Curie-Weiss law with µeff=3.0 µB which is smaller than that of the Nd3+ free ion.
Abstract: Temperature dependence of magnetic susceptibility for superconducting Nd1.5Ba1.5Cu3Oy (Tc~6 K) was measured. The susceptibility of the normal state follows the Curie-Weiss law with µeff=3.0 µB which is smaller than that of the Nd3+ free ion. Susceptibility decreases below 40 K due to the Meissner effect and then increases due to the magnetic effect of the Nd+3 ions.
TL;DR: In this paper, the authors established a phase diagram in the magnetic field-temperature plane and point out similarities to metamagnetic transitions observed in other magnetic systems, such as magnetoresistance.
TL;DR: In this article, the first ferromagnetic quasicrystal was studied and its Curie temperature was about 340K and μ(Fe) = 2.3μB.
Abstract: Paramagnetic, ferromagnetic and antiferromagnetic properties are reported for as-quenched amorphous, annealed quasicrystal and crystal Al-Fe-Ce alloys. The first ferromagnetic quasicrystal was studied. Its Curie temperature is about 340K and μ(Fe) = 2.3μB.
TL;DR: In this article, the results of magnetic susceptibility measurements performed on single crystalline UCu 2 P 2 ferromagnet have been interpreted using a phenomenological approach based on the crystal field model and the molecular field approximation.
TL;DR: For the Curie-Weiss version of the Ising model with random field, this paper showed that the fluctuations have a Gaussian distribution with random (i.e., sample dependent) mean, if the system is away from criticality or at first-order critical points.
Abstract: For the Curie-Weiss version of the Ising Model with random field it is shown that the fluctuations have: i) a Gaussian distribution with random (i. e. sample dependent) mean, if the system is away from criticality or at first-order critical points; ii) a sample-independent non-Gaussian distribution at second- or higher-order critical points.
TL;DR: In this article, the magnetic susceptibility and magnetization of ErBa2Cu3O7−y were analyzed and the critical current density Jc(H) and the reversible magnetization Me(H), which can be explained by the standard theory of paramagnetism with a Brillouin function.
Abstract: We report detailed magnetic susceptibility and magnetization studies for the high Tc oxide superconductor ErBa2Cu3O7−y. The magnetic susceptibility χ of ErBa2Cu3O7−y follows a Curie–Weiss law both above and below Tc with the magnetic moment Peff=9.2μB, which is close to that of 9.58μB deduced from the ground state of Er3+ ion. Magnetization data at various temperatures have revealed a very large magnetic hysteresis. By analyzing the hysteretic magnetization data, we obtain the critical current density Jc(H) and the reversible magnetization Me(H) at 4.2 K. The saturation of Me in high fields at low temperature can be explained by the standard theory of paramagnetism with a Brillouin function. We find that superconductivity and paramagnetism in ErBa2Cu3O7−y exist largely independently of one another.
TL;DR: In this paper, it was shown that when this alloy is rapidly cooled from the melting temperature the iron and aluminium atoms are statistically distributed in three non-equivalent crystallographic sites, i.e. 8i, 8j and 8f.
Abstract: From magnetic studies on YFe6Al6 it was ascertained that both its Curie temperature and its magnetic moment are clearly dependent on thermal treatment (annealing at a temperature of 1073 K) and mechanical treatment (powdering). From tests performed it was concluded that when this alloy is rapidly cooled from the melting temperature the iron and aluminium atoms are statistically distributed in three non-equivalent crystallographic sites, i.e. 8i, 8j and 8f. This alloy is then ferromagnetic with a Curie temperature Tc = 308 K and a magnetic moment of 8.4μB per formula unit at 77.4 K. Annealing or powdering of such an alloy causes changes in the distribution of the iron and aluminium atoms in the crystal lattice (the iron atoms prefer the 8j and 8f sites), which has the effect of lowering the Curie temperature and reducing the magnetic moment of the alloy.
TL;DR: In this article, the authors investigated the magnetic properties of YBa2Cu3O7−Δy as a function of oxygen deficiency Δy and found that the susceptibility in the normal state at low temperatures is dominated by the Curie-Weiss law, while the susceptibility at high temperatures deviates from the CWS.
Abstract: Magnetic properties of YBa2Cu3O7−Δy was investigated by dc- and ac-magnetic susceptibility as a function of oxygen deficiency Δy. The susceptibility in the normal state at low temperatures is dominated by the Curie-Weiss law, while the susceptibility at high temperatures deviates from the Curie-Weiss law. The deviations were successfully explained by assuming the triplet spin-pair excitation from the antiferromagnetically coupled Cu2+ ions in the ground state.
TL;DR: In this article, the magnetic properties of high-Tc superconductors RBa2 Cu3O7−δ with R=Y, Gd were investigated in the temperature range 4.2-300 K.
Abstract: The magnetic properties of high‐Tc superconductors RBa2 Cu3O7−δ with R=Y, Gd were investigated in the temperature range 4.2–300 K. To first order, no interaction was found between superconductivity and paramagnetism in the zero‐field‐cooled state of the Gd‐doped samples: after correction for the Curie–Weiss magnetization, the diamagnetism of these samples is very close to that of the Y‐doped samples. This suggests that the superconducting screening of an applied field has little effect on the field seen by the R species. The diamagnetic screening is found to be strongly time dependent due to flux penetration, whereas the magnetic ions see the applied field without delay.
TL;DR: In this paper, large diamagnetic transitions along with sharp resistive transitions were observed in the LaSr-Nb-O system near room temperature (∼290 K).
Abstract: Large diamagnetic transitions along with sharp resistive transitions were observed in the La-Sr-Nb-O system near room temperature (∼290 K). The amplitude of the diamagnetism reaches 35% of that of a pure Nb sheet. In addition, a behavior similar to weak magnetic spin ordering was observed for some samples at a temperature of about 290 K, over a temperature range of 30 K. The diamagnetism reappears above this temperature and continues up toT ∼320 K. It is not clear what composition ratio of La-Sr-Nb-O is responsible for this large diamagnetism and the high critical temperature. The yield probability of these samples is around 50%. The characteristics of the samples having not passed through many thermal cycles remain stable for about 1 month.
TL;DR: In this paper, a combination of magnetic susceptibility and Mossbauer study is used to establish the fact that there are at least two classes of Mn sites and that Fe substitutes for only one of them.
Abstract: Iron has been successfully incorporated in the quasicrystal i‐Al74Si6Mn20−xFex up to a concentration x=7. A combination of magnetic susceptibility and Mossbauer study establishes the fact that there are at least two ‘‘classes’’ in Mn sites and that Fe substitutes for only one of them. High‐field Mossbauer measurements at 4.2 K show that the substituted iron carries no local moment, while low‐temperature susceptibility data indicate that its presence does not perturb the Curie–Weiss amplitude of the sample. The inference is that both magnetic and nonmagnetic Mn sites must be present in the quasicrystal and that iron can substitute only from among the latter. The simplest interpretation would be in terms of two ‘‘classes’’ on Mn sites (one supporting a local moment, one not), although the possibility of there being more than one class of nonmagnetic site cannot yet be excluded.