Showing papers on "Curie–Weiss law published in 2013"
TL;DR: In this article, the authors used the second-order phase transition theory of second order phase transition (SOPT) to estimate the Curie point temperatures of natural and synthetic magnetic materials.
Abstract: [1] Curie point temperatures (TC) of natural and synthetic magnetic materials are commonly determined in rock magnetism by several measurement methods that can be mutually incompatible and may lead to inconsistent results. Here the common evaluation routines for high-temperature magnetization and magnetic initial susceptibility curves are analyzed and revised based on Landau's theory of second-order phase transitions. It is confirmed that in high-field magnetization curves TC corresponds to the inflection point, below the temperature of maximum curvature or the double-tangent intersection point. At least four different physical processes contribute to the initial magnetic susceptibility near the ordering temperature. They include variation of saturation magnetization, superparamagnetic behavior, magnetization rotation, and magnetic domain wall motion. Because each of these processes may influence the apparent position of TC, initial susceptibility and high-field curves can yield deviating estimates of TC. A new procedure is proposed to efficiently determine the temperature variation of several magnetic parameters on a vibrating-sample magnetometer, by repeatedly measuring quarter-hysteresis loops during a single heating cycle. This procedure takes measurements during the inevitable waiting time necessary for thermal equilibration of the sample, whereby it is not slower than the commonly performed measurements on a Curie balance. However, it returns saturation magnetization, saturation remanence, high-field and low-field slopes, and other parameters as a function of temperature, which provide independent information about TC and other sample properties.
109 citations
TL;DR: In this article, the second-order magnetic transition from ferromagnetic to paramagnetic states at the Curie temperature was investigated, which is quite close to the liquid hydrogen temperature (20.3 K).
Abstract: Magnetic properties and magnetocaloric effects (MCEs) of ternary intermetallic ErFeSi compound have been investigated in detail. It is found that ErFeSi exhibits a second-order magnetic transition from ferromagnetic to paramagnetic states at the Curie temperature TC = 22 K, which is quite close to the liquid hydrogen temperature (20.3 K). A thermomagnetic irreversibility between zero-field-cooling and field-cooling curves is observed below TC in low magnetic field, and it is attributed to the narrow domain wall pinning effect. For a magnetic field change of 5 T, the maximum values of magnetic entropy change (−ΔSM) and adiabatic temperature change (ΔTad) are 23.1 J/kg K and 5.7 K, respectively. Particularly, the values of −ΔSM and refrigerant capacity reach as high as 14.2 J/kg K and 130 J/kg under a magnetic field change of 2 T, respectively. The large MCE without hysteresis loss for relatively low magnetic field change suggests that ErFeSi compound could be a promising material for magnetic refrigeration...
103 citations
TL;DR: In this article, the effect of spin fluctuations on itinerant electron ferromagnetism was extended to include the ferromagnetic phase and the correction to the Hartree-Fock free energy as a function of magnetization was expressed in terms of the transversal dynamical susceptibilities.
Abstract: The theory of the effect of spin fluctuations on itinerant electron ferromagnetism, which we have developed previously, is extended to include the ferromagnetic phase. The correction to the Hartree-Fock free energy as a function of magnetization is expressed in terms of the transversal dynamical susceptibilities and is actually calculated by using a modified random phase approximation for the dynamical susceptibilities; the random phase approximation is modified so as to give a consistent static limit throughout the whole temperature range covering both below and above the Curie point. As a result, the magnetization at low temperatures shows a T 3/2 dependence due to the spin wave excitations, the Curie temperature is generally lowered from the Stoner (Hartree-Fock) value and the magnetic susceptibility above the Curie temperature shows an approximate Curie-Weiss behavior.
87 citations
TL;DR: In this article, the effect of Fe doping on the structural, magnetic and magnetocaloric proprieties in the La0.8Ba0.2Mn1−xFexO3 (0,⩽ ǫxǫµ) perovskites was reported.
57 citations
TL;DR: The Curie-Weiss model is an exact solvable model of ferromagnetism that allows one to study thermodynamic functions in detail, in particular their properties near the critical temperature as discussed by the authors.
Abstract: The Curie–Weiss model is an exactly solvable model of ferromagnetism that allows one to study thermodynamic functions in detail, in particular their properties near the critical temperature. In this model every magnetic moment interacts with every other magnetic moment. Because of its simplicity and the correctness of at least some of its predictions, the Curie–Weiss model occupies an important place in the statistical mechanics literature and its application to information theory. It is frequently presented as an introduction to the Ising model or to spin-glass models, and usually only general features of the Curie–Weiss model are presented. In this paper, we discuss the properties of this model in a rather detailed way. We present the exact, approximate and numerical results for this particular model. The exact expression for the limiting magnetic field is derived.
50 citations
TL;DR: The Curie-Weiss model as discussed by the authors is an exactly soluble model of ferromagnetism that allows one to study in detail the thermodynamic functions, in particular their properties in the neighbourhood of the critical temperature.
Abstract: The Curie-Weiss model is an exactly soluble model of ferromagnetism that allows one to study in detail the thermodynamic functions, in particular their properties in the neighbourhood of the critical temperature. In this model every magnetic moment interacts with every other magnetic moment. Because of its simplicity and because of the correctness of at least of some of its predictions, the Curie-Weiss model occupies an important place in the statistical mechanics literature and its application to information theory. It is frequently presented as an introduction to the Ising model or to spin glass models, and usually only general features of the Curie-Weiss model are presented. We discuss here properties of this model in a rather detailed way. We present the exact, approximate and numerical results for this particular model.
44 citations
TL;DR: In this article, the authors consider stochastic dynamics for a spin system with mean field interaction, in which the interaction potential is subject to noisy and dissipative Stochastic evolution.
Abstract: We consider stochastic dynamics for a spin system with mean field interaction, in which the interaction potential is subject to noisy and dissipative stochastic evolution. We show that, in the thermodynamic limit and at sufficiently low temperature, the magnetization of the system has a time periodic behavior, despite of the fact that no periodic force is applied.
38 citations
TL;DR: In this article, the magnetic properties and magnetocaloric effect in La0.7Sr0.3Mn1−xCoxO3 prepared by conventional solid state reaction have been studied.
Abstract: In this paper, the magnetic properties and magnetocaloric effect in La0.7Sr0.3Mn1−xCoxO3 prepared by conventional solid state reaction have been studied. The samples have rhombohedra crystal structure as was determined by room temperature X-ray diffraction. From the measurements, it was found that the Curie temperature (TC) and magnetic entropy change (ΔSM) are strongly dependent on the Co content. The Curie temperature was found to be 338, 300 and 260 K for x=0, 0.05 and 0.1, respectively. Although the variation of maximum entropy change shows a similar tendency with TC, the phase transition temperatures were widened and the |ΔSM|max values, under a change of the magnetic field of 15 kOe, amount to −1.36, −1.17 and −0.92 J/kg K for x=0, 0.05 and 0.1, respectively. The results suggest that Mn-site substitution should be used to tailor Curie temperature and achieve large relative cooling power (RCP).
37 citations
TL;DR: In this article, the magnetic and electrical properties of the ferromagnetic alloy Co2CrAl in two structural states: (i) after severe plastic deformation and (ii) after short-term high-temperature annealing of the deformed specimens.
Abstract: This paper presents the results of measurements of the magnetic and electrical properties of the ferromagnetic alloy Co2CrAl in two structural states: (i) after severe plastic deformation and (ii) after shortterm high-temperature annealing of the deformed specimens. The experiments have been performed at temperatures in the range from 2 to 900 K in magnetic fields H ≤ 50 kOe. The ferromagnetic Curie temperature TC and the paramagnetic Curie temperature Θ have been determined (TC = 305 K and Θ = 326 K), as well as the spontaneous magnetic moment μS and the effective magnetic moment μeff per molecule of the alloy (μS = 1.62 μB and μeff2 = 8.2 μB2). It has been shown that the magnetic crystalline anisotropy energy of the alloy is on the order of ∼5 × 105 erg/g. The specific features of the electrical properties are associated with the presence of an energy gap in the electronic spectrum near the Fermi level EF and with the change in the parameters of the energy gap as a function of the temperature.
29 citations
TL;DR: In this article, the spontaneous magnetization, high field susceptibility and low temperature irreversible effect were discussed based on a model for the interacting particles consisting of ferrimagnetically aligned core spins and disordered spins in surface layer which become frozen at low temperatures.
27 citations
TL;DR: The recently formulated Landau-Lifshitz-Bloch and self-consistent Bloch equations are capable of addressing some essential features of magnetization dynamics near Curie temperatures as mentioned in this paper.
Abstract: Magnetization dynamics at high temperatures involves both transverse and longitudinal relaxation. The recently formulated Landau-Lifshitz-Bloch and self-consistent Bloch equations are capable of addressing some essential features of magnetization dynamics near Curie temperatures. Here, we analyze these two effective equations in detail and compare their dynamic properties near the Curie temperature.
TL;DR: In this paper, the second-order phase transition for Dy12Co7 has been investigated and the authors found that it induces the complete reversibility of magnetic entropy change around TC, which is very favorable for the application of magnetic refrigeration.
Abstract: Magnetic and magnetocaloric properties of Dy12Co7 compound have been investigated by magnetization measurements. Its magnetization does not reach saturation even for 7 T at 2 K due to the crystalline field effect. Dy12Co7 undergoes a ferromagnetic-paramagnetic phase transition around Curie temperature TC = 64 K. The thermomagnetic irreversibility between the zero-field-cooling and field-cooling curves is detected below TC in low magnetic field, and it is attributed to the narrow domain wall pinning effect. Large magnetic entropy change of 10.0 J kg−1 K−1 and refrigerant capacity of 299 J kg−1 for a magnetic field change of 0–5 T are found around TC, resulting from the large change of magnetization during the magnetic phase transition. The nature of second-order phase transition for Dy12Co7 induces the complete reversibility of magnetic entropy change around TC, which is very favourable for the application of magnetic refrigeration.
TL;DR: In this article, the magnetic properties of the Sr2CoOO4 (SCO) thin film were studied and it was suggested that SCO has electrons with localized character as well as itinerant character.
Abstract: We have studied the magnetic properties of Sr2CoO4 (SCO) thin film. Magnetic hysteresis loops of the film divulge two-phase-like magnetic behavior consisting of hard and soft magnetic phases. Temperature dependent magnetization measurements and time evolution of thermo-remanent magnetization relaxation indicate the possibility of spin-glass dynamics in SCO. The Arrott plots (M2 vs. H/M) exhibit the convex behavior, while the M4 vs. H/M plots show the linear relation near Curie temperature signifying itinerant ferromagnetism in the material, consistent with the calculated Rhodes-Wohlfarth ratio for the film. It is suggested that SCO has electrons with localized character as well as itinerant character.
TL;DR: The hopping integrals obtained from the authors' electronic structure calculations suggest the presence of significant intra-kagome (next-nearest neighbor and diagonal) and inter-k Kagome couplings that take the PbCu3TeO7 system away from a disordered ground state and lead to long-range order, in contrast to what might be expected for an ideal (isotropic) 2D kagome system.
Abstract: We have synthesized polycrystalline and single-crystal samples of PbCu3TeO7 and studied its properties via magnetic susceptibility, χ(T), and heat-capacity, Cp(T), measurements and also electronic structure calculations. Whereas the crystal structure is suggestive of the presence of a quasi-2D network of Cu(2+) (S = 1/2) buckled staircase kagome layers, the χ(T) data show magnetic anisotropy and three magnetic anomalies at temperatures TN1 ∼ 36 K, TN2 ∼ 25 K, and TN3 ∼ 17 K. The χ(T) data follow the Curie-Weiss law above 200 K and a Curie-Weiss temperature θCW ∼- 150 K is obtained. The data deviate from the simple Curie-Weiss law below 200 K, which is well above TN1, suggesting the presence of competing magnetic interactions. The magnetic anomaly at TN3 appears to be of first order from magnetization measurements, although our Cp(T) results do not display any anomaly at TN3. The hopping integrals obtained from our electronic structure calculations suggest the presence of significant intra-kagome (next-nearest neighbor and diagonal) and inter-kagome couplings. These couplings take the PbCu3TeO7 system away from a disordered ground state and lead to long-range order, in contrast to what might be expected for an ideal (isotropic) 2D kagome system.
TL;DR: In this article, a powder X-ray pattern reveals weak superstructure reflections, and the inclusion of additional reflections in the analysis points to a new type of structural arrangement, in a monoclinic system, P21/c space group, a = 7.9663(16) A, b = 4.964(3) A and β = 104.03°.
Abstract: High quality single crystals of EuInGe were grown from the reaction run with excess indium. X-ray diffraction investigations showed that EuInGe crystallizes with a pronounced subcell structure, superstructure of the ThSi2 type: Pnma space group, a = 4.9066(10) A, b = 3.9834(8) A and c = 15.964(3) A. However, the powder X-ray pattern reveals weak superstructure reflections, and the inclusion of additional reflections in the analysis points to a new type of structural arrangement, in a monoclinic system, P21/c space group, a = 7.9663(16) A, b = 4.9119(10) A, c = 16.465(5) A, and β = 104.03°. Magnetization measurements carried out as a function of temperature show multiple magnetic transitions at 13, 25, 44, and 70 K. In the temperature region above 100 K, the Curie–Weiss law is followed indicating a paramagnetic state of the sample. Magnetic moments deduced from this region suggest europium to be in a divalent state, which was further confirmed by 151Eu Mossbauer spectroscopic measurements. Experiments were...
TL;DR: In this article, the temperature variations of the inverse magnetic susceptibility and the inverse intensity of resonance signal obey the Curie-Weiss law and a similarity in temperature variation of the resonance signal width and the adiabatic polaron conductivity points to the polaron mechanism controlling the resonance linewidth.
TL;DR: In this article, the Curie Weiss temperature has been analyzed by a linear extrapolation of the temperature dependence of the magnetization M (T ) curves and the Landau model.
TL;DR: In this article, the effect of Ni substitution on the magnetic properties of polycrystalline Ni2+xMn1−xSn (x = 0, 0.05, and 0.1) Heusler alloys using the magnetization and neutron diffraction measurement techniques.
Abstract: We report the effect of Ni substitution on the magnetic properties of polycrystalline Ni2+xMn1−xSn (x = 0, 0.05, and 0.1) Heusler alloys using the magnetization and neutron diffraction measurement techniques. The paramagnetic to ferromagnetic transition temperature (Curie temperature, TC) has been tuned with the substitution of Ni at the Mn sites (TC≈ 349, 337, and 317 K for x = 0, 0.05, and 0.1 samples, respectively) without a significant reduction in the magnetic entropy change −ΔSM. For a magnetic field change from 0 to 5 T, −ΔSM of 2.9, 2.5, and 2.2 J kg−1 K−1 have been observed for x = 0, 0.05, and 0.1 samples, respectively. From the neutron diffraction study, it has been found that with increasing x, the Mn site ordered moment decreases. −ΔSM as a function of changing magnetic field and Curie temperature follows the molecular mean field model. The studied Ni2+xMn1−xSn alloys, with their nontoxic constituent elements and low-cost, can be used for magnetic cooling over a wide temperature range of 278–...
TL;DR: The structure and magnetic properties of the off-stoichiometric GdNi2Mnx (0.6) alloys have been studied in this paper, where the alloys with 0.
TL;DR: In this paper, the magnetic susceptibilities of the charged particles (proton, electron, and muon) can be larger than that of the neutron, and the effects of anomalous magnetic moments (AMM) of each component on the magnetic susceptibility are examined in detail.
Abstract: The magnetization of neutron star matter in magnetic fields is studied by employing the FSUGold interaction. It is found that the magnetic susceptibilities of the charged particles (proton, electron and muon) can be larger than that of neutron. The effects of the anomalous magnetic moments (AMM) of each component on the magnetic susceptibility are examined in detail. It is found that the proton and electron AMM affect their respective magnetic susceptibility evidently in strong magnetic fields. In addition, they are the protons instead of the electrons that contribute most significantly to the magnetization of the neutron star matter in a relative weak magnetic field, and the induced magnetic field due to the magnetization can be appear to be very large. Finally, the effect of the density-dependent symmetry energy on the magnetization is discussed.
TL;DR: The structural and magnetic properties of the cubic spinel oxide Co2MnO4 (Fd3m space group) doped with different concentrations of bismuth, were investigated by X-ray diffraction and SQUID magnetometry as mentioned in this paper.
TL;DR: In this article, temperature driven magnetization reversal under zero field cooled (ZFC) process in SrRuO3 is observed at very low magnetic field (50 Oe). Magnetization reversal does not exist above 1000 Oe down to 2 K.
Abstract: Temperature driven magnetization reversal under zero field cooled (ZFC) process in SrRuO3 is observed at very low magnetic field (50 Oe). Magnetization reversal does not exist above 1000 Oe down to 2 K. The compensation temperature decreases and the peak in ZFC shifts towards lower temperature with the increase of magnetic field. Magnetic switching behavior is observed below Curie temperature. The normal and inverse magnetocaloric effect at low magnetic field limit coexist in a single compound. Random magnetic state plays a crucial role in ZFC magnetization reversal of SrRuO3.
TL;DR: In this paper, the magnetic properties and magnetoresistance effect of Pb2FeMoO6, synthesized under high pressure at high temperature, were systematically studied and the results showed that the sample showed ferromagnetic behavior with Curie temperature about 243 K.
Abstract: Magnetic properties and magnetoresistance effect of Pb2FeMoO6, synthesized under high pressure at high temperature, were systematically studied. The sample shows ferromagnetic behavior with Curie temperature about 243 K. The field dependent of paramagnetic susceptibility was discussed by the magnetic inhomogeneous related to Fe/Mo ions disorder. Electrical resistivity of the sample exhibits a semiconductor behavior, which can be well understood by variable-range hopping model. A maximum magnetoresistance effect value about 15% was observed at 20 K and 70 kOe. The pronounced linear magnetoresistance effect is attributed to the suppression of spin-fluctuations by the magnetic field.
TL;DR: An orthorhombic DyMnO 3 single crystal has been studied in magnetic fields up to 14 T and between 3 and 4 Kand room temperature as discussed by the authors.
TL;DR: In this paper, the authors show that the strong Cu Cu Cu interactions also present in Gd2BaCuO5, combined with the Gd-Cu interaction, polarize the sublattice giving measurable contributions to the specific heat in the same temperature range.
Abstract: R2BaMO5 (R = Gd, Y and M = Cu, Zn) oxides have been studied by specific heat, dc magnetic susceptibility, and electron paramagnetic resonance (EPR). For one member of the series without magnetic moment at M, namely Gd2BaZnO5, measurements reveal long range antiferromagnetic order at TN(Gd2BaZnO5) = 2.3(0.1)K, much lower than the Curie Weiss temperature of {\Theta}=15.9(0.3)K. This indicates the existence of competing interactions that introduce a large degree of magnetic frustration in the system. For Y2BaCuO5 the Cu Cu interactions are responsible for the broad maximum in the magnetic contribution to the specific heat centered at 18.5(0.01)K that stretches beyond the instrumental limit of 25K. The strong Cu Cu interactions also present in Gd2BaCuO5, combined with the Gd-Cu interaction, polarize the Gd sublattice giving measurable contributions to the specific heat in the same temperature range. In addition, they broaden the Gd EPR line and saturate its integrated intensity. The ordering temperature of Gd ions is raised to TN(Gd2BaCuO5)=12.0(0.1)K.
TL;DR: In this article, the influence of temperature on the magnetic properties and magnetoimpedance of Co64Fe3Cr3Si15B15 and Co67FCr3Si 15B12 amorphous ribbons having different Curie points is studied.
Abstract: The influence of temperature on the magnetic properties and magnetoimpedance of Co64Fe3Cr3Si15B15 and Co67FCr3Si15B12 amorphous ribbons having different Curie points are studied. The impedance and its component are found to change greatly when the ribbons pass into the paramagnetic state. This finding can be used to determine the Curie point of ferromagnets and design high-sensitivity thermal transducers.
TL;DR: In this paper, an extension of the classical Curie-Weiss model is considered, where the global and deterministic external magnetic field is replaced by local and random external fields which interact with each spin of the system.
Abstract: In this paper, we consider an extension of the classical Curie–Weiss model in which the global and deterministic external magnetic field is replaced by local and random external fields which interact with each spin of the system. We prove a large deviations principle for the so-called magnetization per spin Sn/n with respect to the associated Gibbs measure, where Sn/n is the scaled partial sum of spins. In particular, we obtain an explicit expression for the rate function, which enables an extensive study of the phase diagram in some examples. It is worth mentioning that the model considered in this paper covers, in particularly, both the case of i.i.d. random external fields (also known under the name of random field Curie–Weiss models) and the case of dependent random external fields generated by e.g. Markov chains or dynamical systems.
TL;DR: The results of the magnetic moment measurements of the Mn 1− x Ho x S solid solutions at temperatures of 5-300 K in the magnetic field H = 0.05 T are presented in this paper.
TL;DR: The temperature dependence of magnetic susceptibility of the Bi2−ySryIr2O7 system was studied from 2 to 300 K in this paper, where the solid solution (0 ≤ y ≤ 0.9 ) does not show any magnetic transition; however, a noticeable deviation from the Curie-Weiss law occurs and the magnetic behavior of this system can be attributed to short-range magnetic order that is also present in several geometrically frustrated systems.