Showing papers on "Curie–Weiss law published in 2001"
TL;DR: In this article, a table-like behavior was found in the temperature dependence of the magnetic entropy change in soft magnetic GdCoAl alloys, which can be used either to fill up the gap (near 100 K) in the profile of magnetic entropy changes versus temperature required by an eight-stage magnetic refrigerator or to complete an Ericsson circle.
Abstract: Large magnetic entropy changes were observed in RCoAl compounds, where R = Gd, Tb, Dy, and Ho, at their Curie temperatures. These RCoAl alloys have a hexagonal, MgZn2 structure and their Curie temperatures fall in the temperature range 10-100 K. A `table-like' behaviour was found in the temperature dependence of the magnetic entropy change (-ΔS(T)) obtained in the soft magnetic GdCoAl alloys, which can be used either to fill up the gap (near 100 K) in the profile of magnetic entropy change versus temperature required by an eight-stage magnetic refrigerator or to complete an Ericsson circle. It has also been shown that soft ferromagnetic materials with Curie temperatures in the temperature range from 10 K to 100 K can be obtained by using multi-R elements instead of a single-R element in the RCoAl compounds.
108 citations
TL;DR: In this paper, a study of magnetocaloric effect in the Cr-doped colossal magnetoresistance material La 0.67 Sr 0.33 Mn 0.9 Cr 0.1 O 3 was presented.
91 citations
73 citations
TL;DR: The effect of hydrogen and nitrogen insertions on the magnetic properties (Curie temperatures, saturation magnetization, magnetocrystalline anisotropy) of R 2 Fe 17 compounds have been studied by means of X-ray diffraction, torque and pendulum magnetometer techniques and high-field magnetization measurements on single crystals and on magnetically aligned powder samples as mentioned in this paper.
51 citations
TL;DR: The effect of the particle size and ball-mill induced defects on the magnetic properties of cupric oxide has been assessed by magnetic measurements as discussed by the authors, showing that up to room temperature, instead of the increasing susceptibility found in bulk samples, a Curie-Weiss-like behavior is observed above the ordering temperature of ca. 230 K.
49 citations
TL;DR: In this article, single crystal growth and magnetic susceptibility and neutron diffraction studies of the S = 1/2 quasi-1D antiferromagnet CaCu2O3 were reported.
Abstract: We report single crystal growth and magnetic susceptibility and neutron diffraction studies of the S=1/2 quasi-1D antiferromagnet CaCu2O3. The structure of this material is similar to that of the prototype two-leg spin-ladder compound SrCu2O3. However, the Cu-O-Cu bond angle in the ladder rungs in CaCu2O3 is equal to 123 deg, and therefore the magnetic interaction along the rungs is expected to be much weaker in this material. At high temperatures, the magnetic susceptibility of CaCu2O3 can be decomposed into a contribution from 1D antiferromagnetic chains of finite-size chain segments together with a weak Curie contribution. The intrachain magnetic exchange constant, determined from the magnetic susceptibility measurements, is 2000 K. CaCu2O3 undergoes a Neel transition at T_N=25 K with ordering wavevector of (0.429(5), 0.5, 0.5). The magnetic structure is incommensurate in the direction of the frustrated interchain interaction. Weak commensurate (0.5, 0.5, 0.5) magnetic peaks are also observed below T_N. Application of a magnetic field induces a metamagnetic transition at which the incommensurability of the magnetic structure is substantially reduced. The material possesses only short-range magnetic order above the transition field.
46 citations
TL;DR: It is shown that the phenomenon of DD-CSR cross relaxation is absolutely general and to be expected under any electronic configuration.
41 citations
TL;DR: In this article, the magnetic and transport properties of Cr-based III-V diluted magnetic semiconductor Ga1−xCrxAs Cr concentrations up to x=0.10 have been investigated.
Abstract: Magnetic and transport properties of Cr-based III–V diluted magnetic semiconductor Ga1−xCrxAs Cr concentrations up to x=0.10 have been investigated. For all the films, no long-range magnetic order was observed down to 2 K. A sign of paramagnetic Curie temperature is positive, indicating that the dominant magnetic interaction between Cr atoms is ferromagnetic. The effective number of Bohr magneton is estimated to be 5.1±0.4, which is close to that of Cr2+ ion. The magnetization curve shows superparamagnetic behavior at low temperatures. The radius of the local spin order in x=0.034 is estimated to be 1.5–2.0 nm at T=5 K and it decreases with increasing temperature. From Hall effect measurements at room temperature, the magnitude of mobility is estimated to be less than 0.5 cm2/V s. This low mobility strongly suggests that the hopping conductivity is dominant in Ga1−xCrxAs films.
36 citations
TL;DR: In this paper, the exact solution for the one-dimensional Ising model with nearest-neighbour and next-nearest neighbor interactions in an external magnetic field is obtained within the framework of the Kramers-Wannier transfer matrix.
Abstract: The exact solution for the one-dimensional Ising model with nearest-neighbour and next-nearest-neighbour interactions in an external magnetic field is obtained within the framework of the Kramers-Wannier transfer matrix. The explicit analytical expressions for thermodynamic quantities such as magnetization, magnetic susceptibility and specific heat are derived and analyzed at length as functions of temperature, magnetic field, and the signs and values of the interaction parameters.
34 citations
TL;DR: A well-known example is the transition from ferro-to paramagnetism via the magnetic susceptibility as discussed by the authors, defined as the response of magnetization due to the alteration of a magnetic field.
Abstract: Fundamental experiments in magnetism deal with phase transitions. A well-known example is the transition from ferro-to paramagnetism which is commonly observed via the magnetic susceptibility. The susceptibility is defined as the response of magnetization due to the alteration of a magnetic field. Close to the Curie temperature TC the magnetization tends to zero on the average as the ordering effect of the exchange interaction is compensated by the disconcerting action of thermal fluctuations of the spins. Above TC , the ferromagnet becomes paramagnetic. This transition features a very well-pronounced susceptibility peak 1‐ 4 that can be eas
28 citations
TL;DR: In this article, the authors reported dc and ac magnetization of the newly discovered Cd-Mg-RE quasicrystals (RE = Gd, Tb, Dy, Ho, Er, Tm and Yb).
Abstract: We report dc and ac magnetization of the newly discovered Cd-Mg-RE quasicrystals (RE = Gd, Tb, Dy, Ho, Er, Tm and Yb). For all the RE atoms except Yb, the temperature dependence of the dc magnetization obeys the Curie-Weiss law at higher temperatures, T>50 K. Estimated effective moments indicate that these atoms are in the trivalent states. In contrast, the Cd-Mg-Yb quasicrystal shows very small magnetization, suggesting that Yb is in the non-magnetic divalent state. At lower temperatures, spin-glass-like freezing was observed for the RE atoms except Tm and Yb. In particular, the freezing proceeds in two successive steps for RE = Gd, Tb, Dy and Ho, being quite different from canonical spin-glasses.
TL;DR: Magnetic properties of the tetragonal ThMn12-type LaMn4Al8 were investigated to get information on the origin of the large temperature-linear term of the low- temperature specic heat (γ=265 mJ/K2 ) of this compound as discussed by the authors.
TL;DR: Binary REB25 (Gd, Tb, Dy, Ho, Er) B12 icosahedral compounds were successfully synthesized and magnetic properties were measured as discussed by the authors, which revealed that an antiferromagnetic-like transition occurs in TbB25 at 2.1
Abstract: Binary REB25 (RE = Gd, Tb, Dy, Ho, Er) B12 icosahedral compounds were successfully synthesized and magnetic properties were measured. Measurements down to 1.8 K revealed that an antiferromagnetic-like transition occurs in TbB25 at 2.1 K. This transition temperature is almost one order of magnitude lower than that of the transition in the more magnetically dilute TbB50. The structure of TbB25 is refined and, from the differences of structure, the previous conclusion that B12 icosahedra are indicated to play an important role in the transition of TbB50 is further supported. The other magnetic rare-earth compounds show Curie-Weiss behaviour down to the lowest temperatures, with values of the effective moment close to that expected for trivalent rare-earth compounds.
TL;DR: In this paper, the de Haas-van Alphen (dHvA) effect was measured in a single crystal of CeRhSi 3 and of its reference material LaRhSi3 and the results indicated that the 4f-electrons of the SiSi 3 are itinerant.
Abstract: CeRhSi 3 has the large electronic specific-heat coefficient γ = 120 mJ/mol K 2 and the high Kondo temperature T K ∼ 100 K, although its magnetic susceptibility follows the Curie-Weiss law and the specific heat indicates magnetic ordering at 1.8 K. In order to elucidate the 4f-electron nature in CeRhSi 3 , we have grown single crystals of CeRhSi 3 and of its reference material LaRhSi 3 and measured the electrical resistivity, the magnetic susceptibility and the de Haas-van Alphen (dHvA) effect. Comparison of the angular dependence of the dHvA frequency in CeRhSi 3 to that in LaRhSi 3 , indicates that the 4f-electrons of CeRhSi 3 are itinerant.
TL;DR: A La-deficient manganite perovskite sample La0.54Ca0.32MnO3−δ was prepared by conventional solid-state reaction method as discussed by the authors.
Abstract: A La-deficient manganite perovskite sample La0.54Ca0.32MnO3−δ was prepared by conventional solid-state reaction method. The Curie temperature TC is 272 K, about 10 K higher than that of La1−xCaxMnO3. A large magnetic entropy change has been observed and the maximum −ΔSM≈2.9 J/kg K appears at its Curie temperature upon a 0.9 T magnetic field change. The easy fabrication and higher chemical stability make La0.54Ca0.32MnO3−δ a suitable candidate as a working substance in magnetic refrigeration technology.
TL;DR: In this article, a new compound, CaMg2Fe16O27, is synthesized for the first time, in polycrystalline form, using stoichiometric mixture of oxides with standard ceramic technique and characterized by X-ray diffraction.
Abstract: A new compound, CaMg2Fe16O27, is synthesized for the first time, in polycrystalline form, using stoichiometric mixture of oxides with standard ceramic technique and characterized by X-ray diffraction. It is found to have a hexagonal W-type structure with lattice parametersa = 5.850 A andc = 33.156 A. Electrical studies show that the compound is a semiconductor with energy of activation, ΔE = 0.56 eV. Electrical conductivity results show a transition in the conductivity vs temperature plot near the Curie temperature. The activation energy value obtained for the paramagnetic phase is found to be higher than that of the ferrimagnetic phase. The molar magnetic susceptibility was measured in the temperature range 300–850 K and the results show that the compound is ferrimagnetic at room temperature. The compound also shows hysteresis at 300 K. Paramagnetic nature of the sample above Curie temperature is also studied. The Curie molar constantC
M bdcalculated from the plot of 1/χM vsT(K) bdis found to be nearly in agreement with the expected value.
TL;DR: In this article, a number of new pseudo-binary phases GdAl3−xGex were recovered in high yield, and the crystal structures were refined by single crystal X-ray diffraction techniques, and found to vary as a function of rare earth element.
TL;DR: In this paper, the magnetic phase diagram based on the isothermal magnetic field dependence of the DC magnetization at various temperatures for Gd 5 (Si 1.5 Ge 2.5 ) is proposed.
TL;DR: The physical properties of the rare earth bismuthides R5Bi3 (R=Tb, Dy, Ho, Er) and Tb4Bi3 were investigated for the first time as discussed by the authors.
Abstract: The electric conductivity of monazite-type LaCrO4
and zircon-type Nd1 − xCaxCrO4
(x = 0–02)
were characterized by measurements of dc electric conductivity and the Seebeck
coefficient in the 300–600 K range The LaCrO4 and
NdCrO4 were found to be n-type semiconductors, while commonly known
monazite- or zircon-type oxides are insulators In mixed valence compounds
of CrV and CrVI, Nd1 − xCaxCrO4
(x = 01,
02), hole hopping conduction arising from the mixed valency was also
observed The Nd1 − xCaxCrO4
(x = 01,
02) compounds obeyed Curie–Weiss behavior above the Neel
temperature, and the observed magnetic moments for the CrV ions
were in good agreement with the theoretical values Experimental results and
the calculated spin densities by the UHF method indicated that most of the
unpaired electrons from CrV were localized on Cr atoms The ab
initio MO calculations for CrO43− clusters
in NdCrO4 revealed that the SOMO is the degenerate dπ* state
and that the LUMO is the pσ* state (O 2p origin): the
SOMO forms the degenerate states at the top of the valence band and the LUMO
forms a wide conduction band For NdCrO4 and LaCrO4
the electronic conduction mechanism as semiconductors was explained by the
band model For Nd1 − xCaxCrO4
(x = 01,
02) electronic conduction was described by the band model combined with
hopping conduction of holes in degenerate dπ* states It is concluded
that the electronic conductivity of these compounds is caused by an intermixing
of the ligand-to-metal charge-transfer (LMCT) state into the ionic
configuration
TL;DR: In this article, the magnetic properties and magnetoresistance of Pr07Pb03MnO3 single crystals have been studied at low temperature, the temperature dependence of magnetization can be represented as M(T) = M(0)(1-BT3/2) A large B value was observed The spontaneous magnetic moment is slightly larger than the spin-only value for Mn3+ and Mn4+ ions above the Curie temperature.
Abstract: The magnetic properties and magnetoresistance of Pr07Pb03MnO3 single crystals have been studied At low temperature, the temperature dependence of magnetization can be represented as M(T) = M(0)(1-BT3/2) A large B value was observed The spontaneous magnetic moment is slightly larger than the spin-only value for Mn3+ and Mn4+ ions Above the Curie temperature, the susceptibility obeys the Curie-Weiss Law and the resistivity R can fit well with R0exp (T0/T)1/4 It is found that the effective paramagnetic moment obtained from the Curie constant is larger than the theoretical value The large effective paramagnetic moment may originate from the magnetic clusters A large low-field magnetoresistance of ΔR/R(0) = -50% is observed at 230 K in 1 T
TL;DR: In this article, the temperature dependence of the magnetic susceptibility of 6-8 ML Ni/W(1/1/0) was measured in situ in UHV by means of an AC-susceptibility mutual inductance bridge.
TL;DR: In this article, the magnetic susceptibility of Ni1+xTixFe2−2xO4 ferrites was measured over a temperature range of 250-573 K using mutual inductance technique.
TL;DR: In this article, a DTA test was performed within the 300-700 K range, and it was shown that the series of NaNbO3:yMn single crystals exhibit first-order phase transition known from pure sodium niobate.
Abstract: A DTA test, performed within the 300–700 K range, showed that the series of NaNbO3:yMn single crystals exhibit first-order phase transition known from pure sodium niobate. The introduced Mn dopant lowers the temperature of this phase transition at a rate ΔTP–R/Δ%(Mn) ≈ −15 K wt%−1. The electric permittivity measured at ambient pressure showed a clear Curie–Weiss maximum at this antiferroelectric phase transition. The applied axial compression caused gradual suppression of this anomaly towards step-like characteristics. Flat e(T, X, y) curves appeared when the axial pressure X exceeded a few hundreds bars. The stress field was calculated around the Mn ions built into the host. It was pointed out that due to this the stress field and external compression are lower than misfit stress estimated for the P–R structural phase transition and any new phase was not induced with dopant manganese ions at the obtained real concentration y level. The recorded e(T, X, y) characteristics were fitted with a generalized Curie–Weiss formula. It was shown that the molecular field approximation remains valid. Both linear and nonlinear elastic effects were necessary to describe the experimental e(T, X, y) characteristics.
TL;DR: In this paper, low and high-field magnetization measurements and neutron diffraction experiments on Y 1− x Tb x Mn 6 Sn 6 alloys with the hp13-type structure were made.
TL;DR: The averaged over the disordered dynamics for the random field Curie–Weiss model is described, based on spectral asymptotics and includes results on the random fluctuations of eigenvalues and eigenvectors.
Abstract: We describe the averaged over the disordered dynamics for the random field Curie–Weiss model. We consider both the magnetization and the full spin dynamics.Our approach is based on spectral asymptotics and includes results on the random fluctuations of eigenvalues and eigenvectors.
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) and magnetic susceptibility ( χ ) of CeNi 2 Al 3 and of the reference compound YNi 2Al 3 are reported.
TL;DR: The gadolinium phase of the YB 50 structure-type compounds was successfully obtained for the first time by adding silicon as discussed by the authors, which is the first magnetic transition ever observed in the B 12 borides.
TL;DR: In this paper, the properties of the intermetallic compound CePd5Ge3 are discussed in terms of possible Kondo interactions, and some hints on magnetic ordering below 2 K can be deduced from anomalous low temperature behaviour of the magnetisation, resistivity and specific heat.
Journal Article•
TL;DR: In this article, the exact solution of the multi-component Falicov-Kimball model in infinite-dimensions is presented and used to discuss a new fixed point of valence fluctuating intermetallics with Yb and Eu ions.
Abstract: The exact solution of the multi-component Falicov-Kimball model in infinite-dimensions is presented and used to discuss a new fixed point of valence fluctuating intermetallics with Yb and Eu ions. In these compounds, temperature, external magnetic field, pressure, or chemical pressure induce a transition between a metallic state with the f-ions in a mixed-valent (non-magnetic) configuration and a semi-metallic state with the f-ions in an integral-valence (paramagnetic) configuration. The zero-field transition occurs at the temperature Tv, while the zero-temperature transition sets in at the critical field Hc. We present the thermodynamic and dynamic properties of the model for an arbitrary concentration of d- and f-electrons. For large U, we find a MI transition, triggered by the temperature or field-induced change in the f-occupancy.