Condensed state physics demonstrates that the Curie temperature is the point at which spontaneous magnetization drops to zero, marking the critical transition where ferromagnetic or ferrimagnetic materials transform i...Condensed state physics demonstrates that the Curie temperature is the point at which spontaneous magnetization drops to zero, marking the critical transition where ferromagnetic or ferrimagnetic materials transform into paramagnetic substances. Below the Curie temperature, a material remains ferromagnetic;above it, the material becomes paramagnetic, with its magnetic field easily influenced by external magnetic fileds. For example, the Curie temperature of iron (Fe) is 1043 K, while that of neodymium magnets ranges from 583 to 673 K. From both physics and mathematics perspectives, examining the temperature properties of materials is essential, as it provides valuable insights into their electromagnetic and thermodynamic behaviors. This paper makes a bold assumption and, for the first time, carefully verifies the existence of a Casimir temperature at 0.00206 K under conditions of one-atomic spacing.展开更多
Two-dimensional(2D) CrI_(3) is a ferromagnetic semiconductor with potential for applications in spintronics. However,its low Curie temperature(T_(c)) hinders realistic applications of CrI3. Based on first-principles c...Two-dimensional(2D) CrI_(3) is a ferromagnetic semiconductor with potential for applications in spintronics. However,its low Curie temperature(T_(c)) hinders realistic applications of CrI3. Based on first-principles calculations, 5d transition metal(TM) atom doping of CrI_(3)(TM@CrI_(3)) is a universally effective way to increase T_(c), which stems from the increased magnetic moment induced by doping with TM atoms. T_(c) of W@CrI_(3) reaches 254 K, nearly six times higher than that of the host CrI_(3). When the doping concentration of W atoms is increased to above 5.9%, W@CrI_(3) shows room-temperature ferromagnetism. Intriguingly, the large magnetic anisotropy energy of W@CrI_(3) can stabilize the long-range ferromagnetic order. Moreover, TM@CrI_(3) has a strong ferromagnetic stability. All TM@CrI_(3) change from a semiconductor to a halfmetal, except doping with Au atom. These results provide information relevant to potential applications of CrI_(3) monolayers in spintronics.展开更多
Introduction: A thyroid nodule is a localized hypertrophy within the thyroid parenchyma. The aim of our study was to study the benefit of ultrasound in the Ti-rads classification of thyroid nodules. Methodology: This ...Introduction: A thyroid nodule is a localized hypertrophy within the thyroid parenchyma. The aim of our study was to study the benefit of ultrasound in the Ti-rads classification of thyroid nodules. Methodology: This was a prospective study with a descriptive aim, with prospective collection, which took place over a period of 17 months at the “Marie Curie” medical clinic. The ultrasound machine used was a Voluson E8 from 2011 and the examinations were carried out by two radiologists and two experienced sonographers. The parameters studied were sociodemographic data;clinical data and ultrasound aspects of the Ti-rads classification in the management of nodules. Results: We collected 235 patients out of 738 patients referred to the service for a cervical ultrasound, i.e. a frequency of 31.84% of cases. There was a female predominance with 95.7% of cases and a sex ratio of 0.04. The average age of our patients was 50 years. We found on cervical ultrasound: Isthmo-lobar glandular hyperplasia in 99 patients, i.e. a frequency of 42.1%. The Ti-rads 3 classification was the most represented in 69.4% of cases. The benignity criterion represented 85.6% of cases in our patients and the malignancy criterion represented 14.4% of cases. Conclusion: The precise description of a thyroid nodule provided by ultrasound (Ti-rads) is essential in the management of nodules.展开更多
The Kom-Ombo and Nuqra basins in southern Egypt have recently been discovered as potential hydrocarbon basins. The lack of information about the geothermal gradient and heat flow in the study area gives importance to ...The Kom-Ombo and Nuqra basins in southern Egypt have recently been discovered as potential hydrocarbon basins. The lack of information about the geothermal gradient and heat flow in the study area gives importance to studying the heat flow and the geothermal gradient. Several studies were carried out to investigate the geothermal analyses of the northwestern desert, as well as the west and east of the Nile River, using density, compressive wave velocity, and bottom hole temperature (BHT) measured from deep oil wells. This research relies on spectral analysis of airborne magnetic survey data in the Kom-Ombo and Nuqra basins in order to estimate the geothermal gradient based on calculating the depth to the bottom of the magnetic source that caused the occurrence of these magnetic deviations. This depth is equal to the CPD, at which the material loses its magnetic polarisation. This method is fast and gives satisfactory results. Usually, it can be applied as a reconnaissance technique for geothermal exploration targets due to the abundance of magnetic data. The depth of the top (Z<sub>t</sub>) and centroid (Z<sub>0</sub>) of the magnetic source bodies was calculated for the 32 windows representing the study area using spectral analysis of airborne magnetic data. The curie-isotherm depth, geothermal gradient, and heat flow maps were constructed for the study area. The results showed that the CPD in the study area ranges from 13 km to 20 km. The heat flow map values range from 69 to 109 mW/m<sup>2</sup>, with an average of about 80 mW/m<sup>2</sup>. The calculated heat flow values in the assigned areas (A, B, C, and D) of the study area are considered to have high heat flow values, reaching 109 mW/m<sup>2</sup>. On the other hand, the heat flow values in the other parts range from 70 to 85 mW/m<sup>2</sup>. Since heat flow plays an essential role in the maturation of organic matter, it is recommended that hydrocarbon accumulations be located in places with high heat flow values, while deep drilling of hydrocarbon wells is recommended in places with low to moderate heat flow values.展开更多
Piezoelectric ceramics of 0.6(Bi0.9La0.1)FeO3-0.4Pb(Ti1-xMnx)O3 (BLF-PTM) for x=0, 0.01, 0.02, and 0.03 were prepared by sol-gel process combined with a solid-state reaction method. The tan? for BLF-PTM of x=0.01 is j...Piezoelectric ceramics of 0.6(Bi0.9La0.1)FeO3-0.4Pb(Ti1-xMnx)O3 (BLF-PTM) for x=0, 0.01, 0.02, and 0.03 were prepared by sol-gel process combined with a solid-state reaction method. The tan? for BLF-PTM of x=0.01 is just 0.006 at 1 kHz, drastically decreasing by using Mn dopants. The TC increases to 490 ℃ for BLF-PTM of x=0.02. Furthermore, Mn modification effectively enhances the poling state and the piezoelectric properties of BLF-PTM. The kp, Qm, d33, and g33 of 0.34, 403, and 124 pC1·N-1 and 37×10-3 Vm·N-1 are achieved for BLF-PTM of x=0.01. The results indicate that Mn modified BLF-PTM is a competitive high power and high temperature piezoelectric material with excellent piezoelectric properties.展开更多
Magnetic properties and magnetic entropy changes of La（Fe_（1-x）Mn_x）_（11.5）Si_（1.5）H_y compounds are investigated. Their Curie temperatures are adjusted to room temperature by partial Mn substitution for Fe an...Magnetic properties and magnetic entropy changes of La（Fe_（1-x）Mn_x）_（11.5）Si_（1.5）H_y compounds are investigated. Their Curie temperatures are adjusted to room temperature by partial Mn substitution for Fe and hydrogen absorption in 1-atm（1 atm = 1.01325×10~5Pa） hydrogen gas. Under a field change from 0 T to 2 T, the maximum magnetic entropy change for La（Fe_（0.99）Mn_（0.01））_（11.5）Si_（1.5）H_（1.61）is-11.5 J/kg. The suitable Curie temperature and large value of ？S_m make it an attractive potential candidate for the room temperature magnetic refrigeration application.展开更多
The ESR signal of lithium intercalated MCMB can be well simulated by combination of a Lorentz curve and a Gauss curve. The ESR intensity of the Lorentz component is essentially independent of temperature while the Gau...The ESR signal of lithium intercalated MCMB can be well simulated by combination of a Lorentz curve and a Gauss curve. The ESR intensity of the Lorentz component is essentially independent of temperature while the Gauss component shows a linear change with the reciprocal of temperature, indicative of Pauli spin and Curie spin, respectively. The former is probably associated with the ordered (graphitized) structures while the latter with the disordered structures in the sample.展开更多
Measurements of magnetic susceptibility in mechanically alloyed Fe-Ni Invar alloys were taken under pressures up to 7.5GPa. The rate of decrease in the Curie temperature for 700℃ annealed specimen was larger than tha...Measurements of magnetic susceptibility in mechanically alloyed Fe-Ni Invar alloys were taken under pressures up to 7.5GPa. The rate of decrease in the Curie temperature for 700℃ annealed specimen was larger than that annealed at 1000℃. This result can be explained by considering the fact that the width of the concentration fluctuation becomes larger in the specimen annealed at lower temperature.展开更多
We have estimated the DBML（depth to the bottom of the magnetic layer） in South America from the inversion of magnetic anomaly data extracted from the EMAG2 grid. The results show that the DBML values, interpreted as...We have estimated the DBML（depth to the bottom of the magnetic layer） in South America from the inversion of magnetic anomaly data extracted from the EMAG2 grid. The results show that the DBML values, interpreted as the Curie isotherm, vary between -10 and -60 km. The deepest values（〉-45） are mainly observed forming two anomalous zones in the central part of the Andes Cordillera. To the east of the Andes, in most of the stable cratonic area of South America, intermediate values（between -25 and-45 km） are predominant. The shallowest values（〈-25 km） are present in northwestern corner of South America, southern Patagonia, and in a few sectors to the east of the Andes Cordillera. Based on these results, we estimated the heat flow variations along the study area and found a very good correlation with the DBML. Also striking is the observation that the thermal anomalies of low heat flow are closely related to segments of flat subduction, where the presence of a cold and thick subducting oceanic slab beneath the continent, with a virtual absence of hot mantle wedge, leads to a decrease in the heat transfer from the deeper parts of the system.After comparing our results with the Moho depths reported by other authors, we have found that the Curie isotherm is deeper than Moho in most of the South American Platform（northward to -20°S）, which is located in the stable cratonic area at the east of the Andes. This is evidence that the lithospheric mantle here is magnetic and contributes to the long wavelength magnetic signal. Also, our results support the hypothesis that the Curie isotherm may be acting as a boundary above which most of the crustal seismicity is concentrated. Below this boundary the occurrence of seismic events decreases dramatically.展开更多
The magnetization curves at 1.5 K and thermomagnetic curves for amorphous Fe_(90-x)Si_xZr_(10)(x=0,4,7 and 10)alloys prepared by the drum spinning technique have been measured with an extracting sample magnetometer.It...The magnetization curves at 1.5 K and thermomagnetic curves for amorphous Fe_(90-x)Si_xZr_(10)(x=0,4,7 and 10)alloys prepared by the drum spinning technique have been measured with an extracting sample magnetometer.It is obtained that the average magnetic moment,,per magnetic atom and Curie temperature,T_c,in the amorphous FeSiZr alloys increase with increasing Si content.The and T_c are found to be quite small,compared with amorphous FeSiB alloys.This unusual behavior is suggested to be due to the presence of the Fe—Fe antiferromagnetic interactions.The temperature dependence of magnetization at lower temperature is in accordance with Bloch's T^(3/2) law.Calculation shows that the spin wave stiffness constant,D,increases with increasing Si content from 0.37 meV·nm^2 for x=0 to 0.538 meV·nm^2 for x=10.The values of<r^2>indicate that the range of the exchange interaction is roughly the mean atomic distance of nearest neighbours.展开更多
The structure and magnetic properties of Ce 2Co 17-xM x(M=Ga,Al and Si) compounds for M concentrations up to x=5 were studied by means of X-ray diffraction and magnetic measurements. The experimental results show...The structure and magnetic properties of Ce 2Co 17-xM x(M=Ga,Al and Si) compounds for M concentrations up to x=5 were studied by means of X-ray diffraction and magnetic measurements. The experimental results show that the Curie temperatures and Co spontaneous magnetization decrease significantly with increasing the addition of non-magnetic substitutional atoms, and that Si which has a minimum solid solubility in Ce 2Co 17 causes a largest reduction of Curie temperature, spontaneous magnetization and moment per Co atom compared with Ga and Al.展开更多
The FeZrB amorphous alloys for simulating the intergranular amorphous phase in the nanocrystalline Fe 89 Zr 7B 4 soft magnetic materials were obtained by mechanical alloying of a mixture of elemental Fe, Zr and ...The FeZrB amorphous alloys for simulating the intergranular amorphous phase in the nanocrystalline Fe 89 Zr 7B 4 soft magnetic materials were obtained by mechanical alloying of a mixture of elemental Fe, Zr and B powders for 25 h. It is shown that the Curie temperature of the simulated intergranular phase alloy is much lower than that of the intergranular phase with the same chemical composition in the nanocrystalline Fe 89 Zr 7B 4 alloy. The possible mechanism is mainly due to the strong ferromagnetic exchange force among the nanocrystalline α Fe grains.展开更多
The Curie point depth of continental crust can reflect the regional tectonic pattern and geothermal structures. Analysis of magnetism is an efficient way to obtain the Curie point depth on a regional scale. This study...The Curie point depth of continental crust can reflect the regional tectonic pattern and geothermal structures. Analysis of magnetism is an efficient way to obtain the Curie point depth on a regional scale. This study systematically investigated the Curie point depth of Sulu （苏鲁） ultrahigh pressure （UHP） metamorphic belt （33°40＇N to 36°20＇N and 118°E to 120°E, ca. 60 000 km^2）, eastern China using aeromagnetic data. The results show that the Curie point depth of the Sulu region varies from 18.5 to 27 km. The shallowest Curie point depth （ca. 18.5 km） is located in Subei （苏北） subsidence, where the estimated temperature gradient value is about 31.35℃/km, which is comparable with the measured value of 30 ℃/km. In addition, a two-dimensional numerical solution of the heat conduction was used to calculate the temperature field to a depth of 30 km along the profile from Tancheng （郯城） to Lianshui （涟水） with a length of 139 km. The steady state model solved using the finite element method shows that the temperature around the Curie point depth is about 585.36 ℃, which is close to the Curie temperature （580℃） of magnetite at atmospheric pressure. These results provide new insights into the tectonic and continuous thermal structures of the Sulu UHP metamorphic belt.展开更多
オhe effects of composition, annealing temperature and time, annealing heating rate on the Curie temperature of amorphous FeSiB and FeWSiB alloys were studied. The results indicate that the Curie temperature of these ...オhe effects of composition, annealing temperature and time, annealing heating rate on the Curie temperature of amorphous FeSiB and FeWSiB alloys were studied. The results indicate that the Curie temperature of these alloys increases with the increase of the metalloid content when it is <25 at%, then decreases with the further increase of the metalloid content. For amorphous FeSiB and FeWSiB alloys with the low metalloid content, the Curie temperature increases with the annealing temperature and the annealing time. However, for the amorphous FeWSiB alloys with the high metalloid content, the Curie temperature increases at low annealing temperature and with short annealing time, and decreases at high annealing temperature and with long annealing time. The heating rate in measuring Curie temperature also influences the Curie temperature of the alloys. The Curie temperature is higher at lower heating rates.展开更多
Properties of ferroelectric xBiInO3-（1-x）PbTiO3（xBI-（1-x）PT） thin films deposited on（101） SrRuO3/（200）Pt/（200） MgO substrates by rf magnetron sputtering method and effects of deposition conditions are inve...Properties of ferroelectric xBiInO3-（1-x）PbTiO3（xBI-（1-x）PT） thin films deposited on（101） SrRuO3/（200）Pt/（200） MgO substrates by rf magnetron sputtering method and effects of deposition conditions are investigated.The structures of the xBI-（1-x）PT films are characterized by x-ray diffraction and scanning electron microscopy.The results indicate that the thin films are grown with mainly（001） orientation. The chemical compositions of the films are analyzed by scanning electron probe and the results indicate that the loss phenomena of Pb and Bi elements depend on the pressure and temperature during the sputtering process.The sputtering parameters including target composition, substrate temperature, and gas pressure are adjusted to obtain optimum sputtering conditions. To decrease leakage currents,2 mol% La2 O3 is doped in the targets. The P-E hysteresis loops show that the optimized xBI-（1-x）PT（x = 0.24） film has high ferroelectricities with remnant polarization2 Pr = 80μC/cm2 and coercive electric field 2 EC = 300 kV/cm. The Curie temperature is about 640℃. The results show that the films have optimum performance and will have wide applications.展开更多
Using the aeromagnetic data and the method of 3-D magnetic stratum inversion, the data of aeromagnetic anomalies in the investigated region have been processed; and thereby the quantitative buried depth of the Curie i...Using the aeromagnetic data and the method of 3-D magnetic stratum inversion, the data of aeromagnetic anomalies in the investigated region have been processed; and thereby the quantitative buried depth of the Curie isothermal surface in Sichuan Basin and its western marginal area has been obtained. The reliability of the inversion results has been confirmed by the features of regional tectonics, the distribution of geothermal gradient and the results of deep seismic sounding. By analyzing the deep geothermal field, it is concluded that the followings are the environmental conditions for the development and occurrence of earthquakes in the western marginal area of Sichuan Basin: (1) The collision of the Yangtze block with the Sichuan Qinghai block and Kangdian rhombic block has produced strong stress accumulation; and (2) Plastic creep in the middle lower crust owing to the upwelling of mantle flux has provided an adjusting unit for rock rupture and stress release.展开更多
文摘Condensed state physics demonstrates that the Curie temperature is the point at which spontaneous magnetization drops to zero, marking the critical transition where ferromagnetic or ferrimagnetic materials transform into paramagnetic substances. Below the Curie temperature, a material remains ferromagnetic;above it, the material becomes paramagnetic, with its magnetic field easily influenced by external magnetic fileds. For example, the Curie temperature of iron (Fe) is 1043 K, while that of neodymium magnets ranges from 583 to 673 K. From both physics and mathematics perspectives, examining the temperature properties of materials is essential, as it provides valuable insights into their electromagnetic and thermodynamic behaviors. This paper makes a bold assumption and, for the first time, carefully verifies the existence of a Casimir temperature at 0.00206 K under conditions of one-atomic spacing.
文摘Two-dimensional(2D) CrI_(3) is a ferromagnetic semiconductor with potential for applications in spintronics. However,its low Curie temperature(T_(c)) hinders realistic applications of CrI3. Based on first-principles calculations, 5d transition metal(TM) atom doping of CrI_(3)(TM@CrI_(3)) is a universally effective way to increase T_(c), which stems from the increased magnetic moment induced by doping with TM atoms. T_(c) of W@CrI_(3) reaches 254 K, nearly six times higher than that of the host CrI_(3). When the doping concentration of W atoms is increased to above 5.9%, W@CrI_(3) shows room-temperature ferromagnetism. Intriguingly, the large magnetic anisotropy energy of W@CrI_(3) can stabilize the long-range ferromagnetic order. Moreover, TM@CrI_(3) has a strong ferromagnetic stability. All TM@CrI_(3) change from a semiconductor to a halfmetal, except doping with Au atom. These results provide information relevant to potential applications of CrI_(3) monolayers in spintronics.
文摘Introduction: A thyroid nodule is a localized hypertrophy within the thyroid parenchyma. The aim of our study was to study the benefit of ultrasound in the Ti-rads classification of thyroid nodules. Methodology: This was a prospective study with a descriptive aim, with prospective collection, which took place over a period of 17 months at the “Marie Curie” medical clinic. The ultrasound machine used was a Voluson E8 from 2011 and the examinations were carried out by two radiologists and two experienced sonographers. The parameters studied were sociodemographic data;clinical data and ultrasound aspects of the Ti-rads classification in the management of nodules. Results: We collected 235 patients out of 738 patients referred to the service for a cervical ultrasound, i.e. a frequency of 31.84% of cases. There was a female predominance with 95.7% of cases and a sex ratio of 0.04. The average age of our patients was 50 years. We found on cervical ultrasound: Isthmo-lobar glandular hyperplasia in 99 patients, i.e. a frequency of 42.1%. The Ti-rads 3 classification was the most represented in 69.4% of cases. The benignity criterion represented 85.6% of cases in our patients and the malignancy criterion represented 14.4% of cases. Conclusion: The precise description of a thyroid nodule provided by ultrasound (Ti-rads) is essential in the management of nodules.
文摘The Kom-Ombo and Nuqra basins in southern Egypt have recently been discovered as potential hydrocarbon basins. The lack of information about the geothermal gradient and heat flow in the study area gives importance to studying the heat flow and the geothermal gradient. Several studies were carried out to investigate the geothermal analyses of the northwestern desert, as well as the west and east of the Nile River, using density, compressive wave velocity, and bottom hole temperature (BHT) measured from deep oil wells. This research relies on spectral analysis of airborne magnetic survey data in the Kom-Ombo and Nuqra basins in order to estimate the geothermal gradient based on calculating the depth to the bottom of the magnetic source that caused the occurrence of these magnetic deviations. This depth is equal to the CPD, at which the material loses its magnetic polarisation. This method is fast and gives satisfactory results. Usually, it can be applied as a reconnaissance technique for geothermal exploration targets due to the abundance of magnetic data. The depth of the top (Z<sub>t</sub>) and centroid (Z<sub>0</sub>) of the magnetic source bodies was calculated for the 32 windows representing the study area using spectral analysis of airborne magnetic data. The curie-isotherm depth, geothermal gradient, and heat flow maps were constructed for the study area. The results showed that the CPD in the study area ranges from 13 km to 20 km. The heat flow map values range from 69 to 109 mW/m<sup>2</sup>, with an average of about 80 mW/m<sup>2</sup>. The calculated heat flow values in the assigned areas (A, B, C, and D) of the study area are considered to have high heat flow values, reaching 109 mW/m<sup>2</sup>. On the other hand, the heat flow values in the other parts range from 70 to 85 mW/m<sup>2</sup>. Since heat flow plays an essential role in the maturation of organic matter, it is recommended that hydrocarbon accumulations be located in places with high heat flow values, while deep drilling of hydrocarbon wells is recommended in places with low to moderate heat flow values.
基金financially supported by National Nature Science Foundation of China(No.50872080)Shanghai Special Foundation of Nanotechnology(No.1052nm07300)+2 种基金Shanghai Education Development Foundation(No.08SG41)Shanghai Leading Academic Disciplines(No.S30107)Innovational Foundation of Shanghai University
文摘Piezoelectric ceramics of 0.6(Bi0.9La0.1)FeO3-0.4Pb(Ti1-xMnx)O3 (BLF-PTM) for x=0, 0.01, 0.02, and 0.03 were prepared by sol-gel process combined with a solid-state reaction method. The tan? for BLF-PTM of x=0.01 is just 0.006 at 1 kHz, drastically decreasing by using Mn dopants. The TC increases to 490 ℃ for BLF-PTM of x=0.02. Furthermore, Mn modification effectively enhances the poling state and the piezoelectric properties of BLF-PTM. The kp, Qm, d33, and g33 of 0.34, 403, and 124 pC1·N-1 and 37×10-3 Vm·N-1 are achieved for BLF-PTM of x=0.01. The results indicate that Mn modified BLF-PTM is a competitive high power and high temperature piezoelectric material with excellent piezoelectric properties.
基金Projct supported by the Science and Technology Development Fund of Higher Education of Tianjin,China(Grant No.20130301)the Tianjin Research Program of Application Foundation and Advanced Technology,China(Grant No.14JCQNJC4000)
文摘Magnetic properties and magnetic entropy changes of La（Fe_（1-x）Mn_x）_（11.5）Si_（1.5）H_y compounds are investigated. Their Curie temperatures are adjusted to room temperature by partial Mn substitution for Fe and hydrogen absorption in 1-atm（1 atm = 1.01325×10~5Pa） hydrogen gas. Under a field change from 0 T to 2 T, the maximum magnetic entropy change for La（Fe_（0.99）Mn_（0.01））_（11.5）Si_（1.5）H_（1.61）is-11.5 J/kg. The suitable Curie temperature and large value of ？S_m make it an attractive potential candidate for the room temperature magnetic refrigeration application.
基金the National Natural Science Foundation of China (No. 29873034) is gratefully acknowledged. We thank Professor Han Xi YANG and
文摘The ESR signal of lithium intercalated MCMB can be well simulated by combination of a Lorentz curve and a Gauss curve. The ESR intensity of the Lorentz component is essentially independent of temperature while the Gauss component shows a linear change with the reciprocal of temperature, indicative of Pauli spin and Curie spin, respectively. The former is probably associated with the ordered (graphitized) structures while the latter with the disordered structures in the sample.
文摘Measurements of magnetic susceptibility in mechanically alloyed Fe-Ni Invar alloys were taken under pressures up to 7.5GPa. The rate of decrease in the Curie temperature for 700℃ annealed specimen was larger than that annealed at 1000℃. This result can be explained by considering the fact that the width of the concentration fluctuation becomes larger in the specimen annealed at lower temperature.
文摘We have estimated the DBML（depth to the bottom of the magnetic layer） in South America from the inversion of magnetic anomaly data extracted from the EMAG2 grid. The results show that the DBML values, interpreted as the Curie isotherm, vary between -10 and -60 km. The deepest values（〉-45） are mainly observed forming two anomalous zones in the central part of the Andes Cordillera. To the east of the Andes, in most of the stable cratonic area of South America, intermediate values（between -25 and-45 km） are predominant. The shallowest values（〈-25 km） are present in northwestern corner of South America, southern Patagonia, and in a few sectors to the east of the Andes Cordillera. Based on these results, we estimated the heat flow variations along the study area and found a very good correlation with the DBML. Also striking is the observation that the thermal anomalies of low heat flow are closely related to segments of flat subduction, where the presence of a cold and thick subducting oceanic slab beneath the continent, with a virtual absence of hot mantle wedge, leads to a decrease in the heat transfer from the deeper parts of the system.After comparing our results with the Moho depths reported by other authors, we have found that the Curie isotherm is deeper than Moho in most of the South American Platform（northward to -20°S）, which is located in the stable cratonic area at the east of the Andes. This is evidence that the lithospheric mantle here is magnetic and contributes to the long wavelength magnetic signal. Also, our results support the hypothesis that the Curie isotherm may be acting as a boundary above which most of the crustal seismicity is concentrated. Below this boundary the occurrence of seismic events decreases dramatically.
文摘The magnetization curves at 1.5 K and thermomagnetic curves for amorphous Fe_(90-x)Si_xZr_(10)(x=0,4,7 and 10)alloys prepared by the drum spinning technique have been measured with an extracting sample magnetometer.It is obtained that the average magnetic moment,,per magnetic atom and Curie temperature,T_c,in the amorphous FeSiZr alloys increase with increasing Si content.The and T_c are found to be quite small,compared with amorphous FeSiB alloys.This unusual behavior is suggested to be due to the presence of the Fe—Fe antiferromagnetic interactions.The temperature dependence of magnetization at lower temperature is in accordance with Bloch's T^(3/2) law.Calculation shows that the spin wave stiffness constant,D,increases with increasing Si content from 0.37 meV·nm^2 for x=0 to 0.538 meV·nm^2 for x=10.The values of<r^2>indicate that the range of the exchange interaction is roughly the mean atomic distance of nearest neighbours.
文摘The structure and magnetic properties of Ce 2Co 17-xM x(M=Ga,Al and Si) compounds for M concentrations up to x=5 were studied by means of X-ray diffraction and magnetic measurements. The experimental results show that the Curie temperatures and Co spontaneous magnetization decrease significantly with increasing the addition of non-magnetic substitutional atoms, and that Si which has a minimum solid solubility in Ce 2Co 17 causes a largest reduction of Curie temperature, spontaneous magnetization and moment per Co atom compared with Ga and Al.
文摘The FeZrB amorphous alloys for simulating the intergranular amorphous phase in the nanocrystalline Fe 89 Zr 7B 4 soft magnetic materials were obtained by mechanical alloying of a mixture of elemental Fe, Zr and B powders for 25 h. It is shown that the Curie temperature of the simulated intergranular phase alloy is much lower than that of the intergranular phase with the same chemical composition in the nanocrystalline Fe 89 Zr 7B 4 alloy. The possible mechanism is mainly due to the strong ferromagnetic exchange force among the nanocrystalline α Fe grains.
基金Major State Basic Research Development Program of China ("973" Project, No. 2003CB716506)the National Natural Science Foundation of China (No. 40474025).
文摘The Curie point depth of continental crust can reflect the regional tectonic pattern and geothermal structures. Analysis of magnetism is an efficient way to obtain the Curie point depth on a regional scale. This study systematically investigated the Curie point depth of Sulu （苏鲁） ultrahigh pressure （UHP） metamorphic belt （33°40＇N to 36°20＇N and 118°E to 120°E, ca. 60 000 km^2）, eastern China using aeromagnetic data. The results show that the Curie point depth of the Sulu region varies from 18.5 to 27 km. The shallowest Curie point depth （ca. 18.5 km） is located in Subei （苏北） subsidence, where the estimated temperature gradient value is about 31.35℃/km, which is comparable with the measured value of 30 ℃/km. In addition, a two-dimensional numerical solution of the heat conduction was used to calculate the temperature field to a depth of 30 km along the profile from Tancheng （郯城） to Lianshui （涟水） with a length of 139 km. The steady state model solved using the finite element method shows that the temperature around the Curie point depth is about 585.36 ℃, which is close to the Curie temperature （580℃） of magnetite at atmospheric pressure. These results provide new insights into the tectonic and continuous thermal structures of the Sulu UHP metamorphic belt.
文摘オhe effects of composition, annealing temperature and time, annealing heating rate on the Curie temperature of amorphous FeSiB and FeWSiB alloys were studied. The results indicate that the Curie temperature of these alloys increases with the increase of the metalloid content when it is <25 at%, then decreases with the further increase of the metalloid content. For amorphous FeSiB and FeWSiB alloys with the low metalloid content, the Curie temperature increases with the annealing temperature and the annealing time. However, for the amorphous FeWSiB alloys with the high metalloid content, the Curie temperature increases at low annealing temperature and with short annealing time, and decreases at high annealing temperature and with long annealing time. The heating rate in measuring Curie temperature also influences the Curie temperature of the alloys. The Curie temperature is higher at lower heating rates.
基金Supported by the National Natural Science Foundation of China under Grant No 11304160the Special Fund for Public Interest of China under Grant No 201510068,and the NUPTFC under Grant No NY215111
文摘Properties of ferroelectric xBiInO3-（1-x）PbTiO3（xBI-（1-x）PT） thin films deposited on（101） SrRuO3/（200）Pt/（200） MgO substrates by rf magnetron sputtering method and effects of deposition conditions are investigated.The structures of the xBI-（1-x）PT films are characterized by x-ray diffraction and scanning electron microscopy.The results indicate that the thin films are grown with mainly（001） orientation. The chemical compositions of the films are analyzed by scanning electron probe and the results indicate that the loss phenomena of Pb and Bi elements depend on the pressure and temperature during the sputtering process.The sputtering parameters including target composition, substrate temperature, and gas pressure are adjusted to obtain optimum sputtering conditions. To decrease leakage currents,2 mol% La2 O3 is doped in the targets. The P-E hysteresis loops show that the optimized xBI-（1-x）PT（x = 0.24） film has high ferroelectricities with remnant polarization2 Pr = 80μC/cm2 and coercive electric field 2 EC = 300 kV/cm. The Curie temperature is about 640℃. The results show that the films have optimum performance and will have wide applications.
文摘Using the aeromagnetic data and the method of 3-D magnetic stratum inversion, the data of aeromagnetic anomalies in the investigated region have been processed; and thereby the quantitative buried depth of the Curie isothermal surface in Sichuan Basin and its western marginal area has been obtained. The reliability of the inversion results has been confirmed by the features of regional tectonics, the distribution of geothermal gradient and the results of deep seismic sounding. By analyzing the deep geothermal field, it is concluded that the followings are the environmental conditions for the development and occurrence of earthquakes in the western marginal area of Sichuan Basin: (1) The collision of the Yangtze block with the Sichuan Qinghai block and Kangdian rhombic block has produced strong stress accumulation; and (2) Plastic creep in the middle lower crust owing to the upwelling of mantle flux has provided an adjusting unit for rock rupture and stress release.
