The Experts below are selected from a list of 122229 Experts worldwide ranked by ideXlab platform
Jian Wang - One of the best experts on this subject based on the ideXlab platform.
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Curie point depths in northeast china and their geothermal implications for the songliao basin
Journal of Asian Earth Sciences, 2018Co-Authors: Jian WangAbstract:Abstract This work integrates processing and interpretation of the combined geomagnetic anomaly model of NGDC-720-V3.1 to better constrain thermal structures of the Northeast China lithosphere, which shows intensive extension and active volcanism during the Mesozoic and Cenozoic. Numerical tests demonstrate that magnetic anomalies calculated at 20 km altitude can be used for accurate Curie depth estimation. Averaged Curie depths using a 3D fractal exponent of 3.0 vary from ∼ 13 ± 2.0 to 33 ± 4.1 km with a mean of ∼ 22 ± 2.4 km in Northeast China. With temperature-dependent thermal conductivity models constrained by incorporated surface heat flow and Curie depths in different geological blocks, the thermal lithospheric thicknesses are estimated mostly between 45 and 90 km based on 1D steady-state thermal conduction equation. Beneath the Songliao Basin, the Moho temperatures are abnormally high, ranging from ca. 700 to 1000 °C, and the mantle contributes about 65% of the total surface heat flow. The shallow Curie points and thermal lithosphere-asthenosphere boundary, together with high Moho temperatures and mantle heat flow, support abnormally high geotherms in the Songliao Basin, originated from hot upper mantle upwelling triggered likely by lithospheric delamination.
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a global reference model of Curie point depths based on emag2
Scientific Reports, 2017Co-Authors: Jian WangAbstract:In this paper, we use a robust inversion algorithm, which we have tested in many regional studies, to obtain the first global model of Curie-point depth (GCDM) from magnetic anomaly inversion based on fractal magnetization. Statistically, the oceanic Curie depth mean is smaller than the continental one, but continental Curie depths are almost bimodal, showing shallow Curie points in some old cratons. Oceanic Curie depths show modifications by hydrothermal circulations in young oceanic lithosphere and thermal perturbations in old oceanic lithosphere. Oceanic Curie depths also show strong dependence on the spreading rate along active spreading centers. Curie depths and heat flow are correlated, following optimal theoretical curves of average thermal conductivities K = ~2.0 W(m°C)−1 for the ocean and K = ~2.5 W(m°C)−1 for the continent. The calculated heat flow from Curie depths and large-interval gridding of measured heat flow all indicate that the global heat flow average is about 70.0 mW/m2, leading to a global heat loss ranging from ~34.6 to 36.6 TW.
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thermal evolution of the north atlantic lithosphere new constraints from magnetic anomaly inversion with a fractal magnetization model
Geochemistry Geophysics Geosystems, 2013Co-Authors: Jian Wang, Jian Lin, Tingting WangAbstract:[1] Using recently published global magnetic models, we present the first independent constraint on North Atlantic geothermal state and mantle dynamics from magnetic anomaly inversion with a fractal magnetization model. Two theoretical models of radial amplitude spectrum of magnetic anomalies are found almost identical, and both are applicable to detecting Curie depths in using the centroid method based on spectral linearization at certain wave number bands. Theoretical and numerical studies confirm the robustness of this inversion scheme. A fractal exponent of 3.0 in the magnetic susceptibility is found suitable, and Curie depths are well constrained by their known depths near the mid-Atlantic ridge. While generally increasing with growing ages, North Atlantic Curie depths show large oscillating and heterogeneous patterns related most likely to small-scale sublithospheric convections, which are found to have an onset time around 40 Ma and a scale of about 500 km, and are in preferred transverse rolls. Hotspots in North Atlantic also contribute to large geothermal and Curie-depth variations, but they appear to connect more closely to geochemical anomalies or small-scale convection than to mantle plumes. Curie depths can be correlated to heat flow gridded in a constant 1° interval, which reveals decreasing effective thermal conductivity with depths within the magnetic layer. North Atlantic Curie points are mostly beneath the Moho, suggesting that the uppermost mantle is magnetized from serpentinization and induces long-wavelength magnetic anomalies. Small-scale convection and serpentinization together may cause apparent flattening and deviations in heat flow and bathymetry from theoretical cooling models in old oceanic lithosphere.
Kazunori Sato - One of the best experts on this subject based on the ideXlab platform.
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theoretical prediction of Curie temperature in zn cr s zn cr se and zn cr te by first principles calculations
Japanese Journal of Applied Physics, 2004Co-Authors: Tetsuya Fukushima, Kazunori Sato, Hiroshi Katayamayoshida, P H DederichsAbstract:The electronic structure and the magnetic properties of (Zn,Cr)S, (Zn,Cr)Se and (Zn,Cr)Te are calculated by using the Korringa-Kohn-Rostoker method combined with the coherent potential approximation (KKR-CPA) within the local density approximation. Curie temperatures are calculated by the mean field approximation (MFA) and by Monte Carlo simulation. It is found that the MFA strongly overestimates the Curie temperatures for low concentrations due to shortrangeness of interactions in (Zn,Cr)S, (Zn,Cr)Se and (Zn,Cr)Te. The Curie temperatures of (Zn,Cr)Te calculated by Monte Carlo simulation agree very well with recent experimental values.
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Curie temperatures of iii v diluted magnetic semiconductors calculated from first principles
EPL, 2003Co-Authors: Kazunori Sato, P H Dederics, Hiroshi KatayamayoshidaAbstract:Curie temperatures of the diluted magnetic semiconductors (Ga, Mn)As, (Ga, Mn)N, (Ga, Cr)As and (Ga, Cr)N are evaluated from first principles. The electronic structure is calculated in the local spin density approximation by using the Korringa-Kohn-Rostoker method combined with the coherent potential approximation to describe the substitutional and spin disorder. From the total energy differences between the ferromagnetic state and the spin-glass state, realistic estimations of Curie temperatures are achieved by using a mapping on the Heisenberg model in the mean-field approximation. Effects of additional carrier doping treatments are also investigated. Very large Curie temperatures are obtained, lying above room temperature for (Ga, Mn)N, (Ga, Cr)As and (Ga, Cr)N. Upon hole doping the Curie temperature of (Ga, Mn)N further increases, while (Ga, Mn)As shows a plateau behavior.
O Matsubayashi - One of the best experts on this subject based on the ideXlab platform.
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Curie point depth based on spectrum analysis of the magnetic anomaly data in east and southeast asia
Tectonophysics, 1999Co-Authors: Akiko Tanaka, Y Okubo, O MatsubayashiAbstract:Abstract The bottom of the magnetized crust determined from the spectral analysis of residual magnetic anomalies is generally interpreted as the level of the Curie point isotherm. A method to estimate the depth extent of magnetic sources (Curie point depth analysis) was applied to the magnetic anomalies of East and Southeast Asia. Although the geologic and physiographic complexities of this area constrain the method, certain correlations between the Curie point depths and heat flow data are apparent and the Curie point depths are consistent with the tectonic settings. Shallow basal depths of magnetic sources that extend in back-arc regions correspond to high heat flow values. The correspondence of deep basal depths with low heat flow values along the trench axis suggests that they are both related to the subducting plate. We also estimate the Curie point depths from heat flow data using a one-dimensional heat conductive transport model. Good agreement between the Curie point depths derived from heat flow data and magnetic data suggests that the Curie point depth analysis is useful to estimate the regional thermal structure.
P Bruno - One of the best experts on this subject based on the ideXlab platform.
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pressure dependence of the Curie temperature in ni 2 mnsn heusler alloy a first principles study
Physical Review B, 2005Co-Authors: E şasioglu, L M Sandratskii, P BrunoAbstract:The pressure dependence of electronic structure, exchange interactions, and Curie temperature in the ferromagnetic Heusler alloy ${\mathrm{Ni}}_{2}\mathrm{MnSn}$ has been studied theoretically within the framework of the density-functional theory. The calculation of the exchange parameters is based on the frozen-magnon approach. The Curie temperature ${T}_{c}$ is calculated within the mean-field approximation by solving the matrix equation for a multisublattice system. In agrement with experiment the Curie temperature increased from 362 K at ambient pressure to 396 K at 12 GPa. Extending the variation of the lattice parameter beyond the range studied experimentally, we obtained nonmonotonic pressure dependence of the Curie temperature and metamagnetic transition. We relate the theoretical dependence of ${T}_{c}$ on the lattice constant to the corresponding dependence predicted by the empirical interaction curve. The Mn-Ni atomic interchange observed experimentally is simulated to study its influence on the Curie temperature.
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first principles calculation of the intersublattice exchange interactions and Curie temperatures of the full heusler alloysni2mnx x ga in sn sb
Physical Review B, 2004Co-Authors: E şasioglu, L M Sandratskii, P BrunoAbstract:The interatomic exchange interactions and Curie temperatures in $\mathrm{Ni}$-based full Heusler alloys ${\mathrm{Ni}}_{2}\mathrm{Mn}X$ with $X=\mathrm{Ga},\mathrm{In},\mathrm{Sn}$, and $\mathrm{Sb}$ are studied within the framework of the density-functional theory. The calculation of the exchange parameters is based on the frozen-magnon approach. Despite closeness of the experimental Curie temperatures for all four systems, their magnetism appeared to differ strongly. This difference involves both the $\mathrm{Mn}\text{\ensuremath{-}}\mathrm{Mn}$ and $\mathrm{Mn}\text{\ensuremath{-}}\mathrm{Ni}$ exchange interactions. The Curie temperatures, ${T}_{C}$, are calculated within the mean-field approximation by solving a matrix equation for a multisublattice system. Good agreement with experiment for all four systems is obtained. The role of different exchange interactions in the formation of ${T}_{C}$ of the systems is discussed.
X X Zhang - One of the best experts on this subject based on the ideXlab platform.
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giant magnetocaloric effect in isostructural mnnige conige system by establishing a Curie temperature window
Applied Physics Letters, 2013Co-Authors: Enke Liu, Hongguo Zhang, Xiaoming Zhang, W H Wang, J L Chen, H W Zhang, L Feng, X X ZhangAbstract:An effective scheme of isostructural alloying was applied to establish a Curie-temperature window in isostructural MnNiGe-CoNiGe system. With the simultaneous accomplishment of decreasing structural-transition temperature and converting antiferromagnetic martensite to ferromagnetic state, a 200 K Curie-temperature window was established between Curie temperatures of austenite and martensite phases. In the window, a first-order magnetostructural transition between paramagnetic austenite and ferromagnetic martensite occurs with a sharp jump in magnetization, showing a magnetic entropy change as large as −40 J kg−1 K−1 in a 50 kOe field change. This giant magnetocaloric effect enables Mn1−xCoxNiGe to become a potential magnetic refrigerant.
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magnetic entropy change in rcoal r gd tb dy and ho compounds candidate materials for providing magnetic refrigeration in the temperature range 10 k to 100 k
Journal of Physics: Condensed Matter, 2001Co-Authors: X X Zhang, Fei Wang, G H WenAbstract: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.
