This study presents the influence of Zn and Nd co-substitution on structure,morphology,AC susceptibility and ZFC-FC magnetizations of Sr nanohexaferrites(NHFs),SrFe12-x(Zn,Nd)xO19(0.0≤x≤1.0),which was produced by so...This study presents the influence of Zn and Nd co-substitution on structure,morphology,AC susceptibility and ZFC-FC magnetizations of Sr nanohexaferrites(NHFs),SrFe12-x(Zn,Nd)xO19(0.0≤x≤1.0),which was produced by sol-gel approach.XRD powder patterns,scanning electron microscopy(SEM) and high-resolution transmission electron spectroscopy(HR-TEM) approve the synthesis of Sr M-type hexaferrite.Mossbauer spectra show that Zn^2+ions occupy 2 b and 4f1 sites while Nd3+ions locate at 2 a,4f2 and 12 k sites.The magnetic properties of the produced Sr-NHFs were investigated also by ZFC-FC magnetizations and AC susceptibility.According to the MFC-MZFC results(between 2 and 400 K),no blocking temperature was detected which indicates the ferromagnetic(FM) behavior of NHFs.At lower temperatures,a super-spin glass like behavior is discerned.The AC susceptibility indicates that the magnetic interactions are improved due to the inclusion of low content(x=0.1) of Nd^3+and Zn^2+ions into the Sr-NHFs.However,with further increasing the Nd^3+and Zn^2+contents(x=0.9),the magnetic interactions are weakened.展开更多
Spinel Li CoMnO4 is prepared by solid-state reaction and its magnetic properties are comprehensively studied by direct current（DC） and alternating current（AC） susceptibilities, isothermal remanent magnetizations, ...Spinel Li CoMnO4 is prepared by solid-state reaction and its magnetic properties are comprehensively studied by direct current（DC） and alternating current（AC） susceptibilities, isothermal remanent magnetizations, and magnetic hysteresis.Fitting to the Curie–Weiss law by using high-temperature zero-field-cooled susceptibility confirms a low-spin state of Co^3＋with S = 0. Both the fitting parameters first increase and then tend to be saturated at high magnetic fields through using isothermal remanent magnetizations, which suggests a spin glass transition at low temperature. AC susceptibility study also supports this conclusion since the frequency dependence of peak position and intensity follows the tendency of a spin glass transition. The origin of the spin-glass transition in Li CoMnO4 might be attributed to a spatial segregation between non-magnetic Co^3＋regions and spin glass ordered regions of Mn^4＋ions.展开更多
In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high Tc superconductors. It is fou...In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high Tc superconductors. It is found that the dc current-voltage characteristic of mixed state superconductors has a general form of extended power law which is based on the Ginzburg-Landau （GL） functional in the similar way as the vortex glass theory. Isotherms simulated from this nonlinear equation fit the experimental I- V data of Strachan et al. [Phys. Rev. Left. 87（2001） 067007]. The puzzling question of the derivative plot for the I - V curves and the controversy surrounding the values of critical exponents are discussed.展开更多
A reliable prediction of AC loss is essential for the application of International Thermonuclear Experimental Reactor(ITER) cable-in-conduit conductors(CICCs);however,the calculation of AC loss of ITER CICCs is a cumb...A reliable prediction of AC loss is essential for the application of International Thermonuclear Experimental Reactor(ITER) cable-in-conduit conductors(CICCs);however,the calculation of AC loss of ITER CICCs is a cumbersome task due to the complicated geometry of the multistage cables and the extreme operating conditions in ITER.In this paper,we described the models developed for hysteresis and coupling loss calculation,which can be suitable for the construction of ITER magnetic system.Meanwhile,we compared the results of theoretical analysis with the SULTAN test result to evaluate the numerical model we used.In addition,we introduced the n-value and AC loss with transport current for CICCs based on the DC measurement results at SULTAN,which lays the foundation for the further study.展开更多
Crystals of Tl-2223 and Tl-2212 have been successfully grown by self-flux method. The typical dimension in 1.0×1.0×0.1 mm3, and crystals as big as 2.0×2.0×0.3mm3 were also obtained. The transition ...Crystals of Tl-2223 and Tl-2212 have been successfully grown by self-flux method. The typical dimension in 1.0×1.0×0.1 mm3, and crystals as big as 2.0×2.0×0.3mm3 were also obtained. The transition temperature of crystals of Tl-2212 and Tl-2223 were 110 and 119K, respectively. Detailed studies on the effect of the cooling rate as well as Tl content were conducted. The results of X-ray diffraction experiments, SEM and EDX are also presented. AC susceptibility measurements were carried out on a Tl-2212 single crystal under various external magnetic fields applied normal to a-b plane. Measurements of reflectance spectra were also applied to a single crystal of Tl-2223 to investigate the optical anisotropy of Tl-2223.展开更多
The amplitude-dependent ac susceptibility of high-temperature superconductors is shown to obey some empirical scaling relations. We try to analyze this behavior by extending a dc nonlinear response function of mixed s...The amplitude-dependent ac susceptibility of high-temperature superconductors is shown to obey some empirical scaling relations. We try to analyze this behavior by extending a dc nonlinear response function of mixed state to the ac cases. The derived equations for critical current and ac susceptibility x(T) agree with the scaling relations of experimental data.展开更多
Ac susceptibility at low temperatures of Pro.75Nao.25MnO3-xFexO3 （0 ≤ x ≤0.30） is investigated. The peak value of the real component of ac susceptibility X＇ at the freezing temperature Tf is suppressed with the i...Ac susceptibility at low temperatures of Pro.75Nao.25MnO3-xFexO3 （0 ≤ x ≤0.30） is investigated. The peak value of the real component of ac susceptibility X＇ at the freezing temperature Tf is suppressed with the increasing frequency. The peak value of X＇ shows a linear relation between Tf and the logarithm of the frequency ω. The normalized slope P = △Tf/Tf△lgco, which is much lower than canonical insulating spin glass systems in which 0.06 ≤ P ≤ 0,08. The peak value of the imaginary component of the ac susceptibility X＂ at Tf for the x= 0, 0.02, 0.30 samples increases with increasing frequency, suggesting a cluster glass ground state with a coexistence of charge-ordered phase and correlated ferromagnetic clusters in spin glass matrix. The peak value ofx＂ at Tf for the x = 0.10 sample decreases with increasing frequency, suggesting a phase separation ground state. The peak value of X＂at Tf for the x = 0.05 sample decreases with increasing frequency for ω ≤52 Hz and increases subsequently till 701 Hz, and then decreases with further increasing frequency for ω ≥ 1501 Hz. This complex behaviour is ascribed to the competition between the effects of large and little ferromagnetic clusters in the sample. The ground state of x = 0.05 sample is a transition state from cluster glass to phase separation.展开更多
The effects of Nd2O3 nanoparticles addition on microstructure, transport and AC susceptibility properties of YBa2Cu3O7–δ（Y123） superconductors were systematically investigated using X-ray diffraction （XRD）, scan...The effects of Nd2O3 nanoparticles addition on microstructure, transport and AC susceptibility properties of YBa2Cu3O7–δ（Y123） superconductors were systematically investigated using X-ray diffraction （XRD）, scanning electron micrograph （SEM）, four point probe measurement and AC spectrometer. It was found that the added samples were predominant by Y-123 phase beside small amount of Y-211 and unreacted Nd2O3secondary phases. All added samples preserved the orthorhombic structure similar to the pure sample and no orthorhombic-to-tetragonal transition occurred. The samples became more porous and their grain size significantly de-creased with addition of Nd2O3. The addition of nano-Nd2O3 disturbed the grain growth of Y123, thus resulting in the degradation of superconducting properties of the samples. The superconducting transition temperature （Tc onset） of samples decreased from 92 K for x=0.0 to 78 K forx=1.0 wt.%, which could be attributable to oxygen vacancy disorder. From AC susceptibility result, the inter- and intra-granular loss peaks became wider and broader with increase of Nd2O3 addition due to the weakening of grains coupling. On the other hand, the inter-granular critical current density,Jcm, was found to increase with Nd2O3 addition and had the highest value at x=0.6, confirming that Nd2O3 nanoparticles acted as pinning centers in Y123 matrix.展开更多
In this research two samples of a nominal composition Bi1.6Pb0.4Sr2Ca2Cu3Ox were prepared by the solid state reaction method, using two different routes. Codes A and B are used to refer to the two samples. In preparin...In this research two samples of a nominal composition Bi1.6Pb0.4Sr2Ca2Cu3Ox were prepared by the solid state reaction method, using two different routes. Codes A and B are used to refer to the two samples. In preparing sample A, the standard method for calcination was used, while for sample B, the SrCO3 and CaCO3 were calcinated at 1100℃ for 3 h. Calcination was done separately on SrCO3 and CaCO3 in order to eliminate CO2. Then after mixing and grinding, the powder mixtures of Bi2O3, CuO, PbO, SrO and CaO were calcinated at 840℃ for 70 h. Also, the samples (samples C) of nominal compositions Bi1.6Pb0.4Sr2Ca2Cu3Ox+ % x Gd2O3 (% x = 0, 3, 5, 7 and 9) have been synthesized by this method. The XRD and SEM results show that addition of Gd2O3 helps to increase the amount of Bi-2212 phase, while alternative calcination process improves the formation of the Bi-2223 phase. In addition, the AC susceptibility measurements confirm the XRD and SEM results.展开更多
Single phase polycrystalline samples Na0.7Co1-xAlxO2 （x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 030） were prepared by solid state reaction. The magnetic properties from 5 K to 300 K have been studied by dc and ac magneti...Single phase polycrystalline samples Na0.7Co1-xAlxO2 （x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 030） were prepared by solid state reaction. The magnetic properties from 5 K to 300 K have been studied by dc and ac magnetic susceptibility measurements. Samples with lower doping quantity （x = 0, 0.05, 0.10） showed paramagnetic behaviors, but those with higher doping quantity （x=0.20, 0.25, 0.30）showed spin-glass behaviors with a freezing temperature （Tf） of about 13 K.展开更多
基金supported by the Institute for Research&Medical Consultations(IRMC)of Imam Abdulrahman Bin Faisal University(IAU-Saudi Arabia)(2017-IRMC-S-3,2018-IRMC-S-1,2018-IRMC-S-2).
文摘This study presents the influence of Zn and Nd co-substitution on structure,morphology,AC susceptibility and ZFC-FC magnetizations of Sr nanohexaferrites(NHFs),SrFe12-x(Zn,Nd)xO19(0.0≤x≤1.0),which was produced by sol-gel approach.XRD powder patterns,scanning electron microscopy(SEM) and high-resolution transmission electron spectroscopy(HR-TEM) approve the synthesis of Sr M-type hexaferrite.Mossbauer spectra show that Zn^2+ions occupy 2 b and 4f1 sites while Nd3+ions locate at 2 a,4f2 and 12 k sites.The magnetic properties of the produced Sr-NHFs were investigated also by ZFC-FC magnetizations and AC susceptibility.According to the MFC-MZFC results(between 2 and 400 K),no blocking temperature was detected which indicates the ferromagnetic(FM) behavior of NHFs.At lower temperatures,a super-spin glass like behavior is discerned.The AC susceptibility indicates that the magnetic interactions are improved due to the inclusion of low content(x=0.1) of Nd^3+and Zn^2+ions into the Sr-NHFs.However,with further increasing the Nd^3+and Zn^2+contents(x=0.9),the magnetic interactions are weakened.
基金Project supported by the National Key Basic Research Program of China(Grant No.2015CB251103)the Development Program of Science and Technology of Jilin Province+2 种基金China(Grant No.20140101093JC)the Program of Science and Technology of Jilin CityChina(Grant No.201434006)
文摘Spinel Li CoMnO4 is prepared by solid-state reaction and its magnetic properties are comprehensively studied by direct current（DC） and alternating current（AC） susceptibilities, isothermal remanent magnetizations, and magnetic hysteresis.Fitting to the Curie–Weiss law by using high-temperature zero-field-cooled susceptibility confirms a low-spin state of Co^3＋with S = 0. Both the fitting parameters first increase and then tend to be saturated at high magnetic fields through using isothermal remanent magnetizations, which suggests a spin glass transition at low temperature. AC susceptibility study also supports this conclusion since the frequency dependence of peak position and intensity follows the tendency of a spin glass transition. The origin of the spin-glass transition in Li CoMnO4 might be attributed to a spatial segregation between non-magnetic Co^3＋regions and spin glass ordered regions of Mn^4＋ions.
基金Supported by the National Key Basic Research Special Foundation of China under Grant No G1999064602, and the Natlonal Natural Science Foundation of China under Grant Nos 10174003, 50377040 and 90303008.
文摘In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high Tc superconductors. It is found that the dc current-voltage characteristic of mixed state superconductors has a general form of extended power law which is based on the Ginzburg-Landau （GL） functional in the similar way as the vortex glass theory. Isotherms simulated from this nonlinear equation fit the experimental I- V data of Strachan et al. [Phys. Rev. Left. 87（2001） 067007]. The puzzling question of the derivative plot for the I - V curves and the controversy surrounding the values of critical exponents are discussed.
基金supported in part by Ministry of Science and Technology of China under Grant 2014GB105001
文摘A reliable prediction of AC loss is essential for the application of International Thermonuclear Experimental Reactor(ITER) cable-in-conduit conductors(CICCs);however,the calculation of AC loss of ITER CICCs is a cumbersome task due to the complicated geometry of the multistage cables and the extreme operating conditions in ITER.In this paper,we described the models developed for hysteresis and coupling loss calculation,which can be suitable for the construction of ITER magnetic system.Meanwhile,we compared the results of theoretical analysis with the SULTAN test result to evaluate the numerical model we used.In addition,we introduced the n-value and AC loss with transport current for CICCs based on the DC measurement results at SULTAN,which lays the foundation for the further study.
文摘Crystals of Tl-2223 and Tl-2212 have been successfully grown by self-flux method. The typical dimension in 1.0×1.0×0.1 mm3, and crystals as big as 2.0×2.0×0.3mm3 were also obtained. The transition temperature of crystals of Tl-2212 and Tl-2223 were 110 and 119K, respectively. Detailed studies on the effect of the cooling rate as well as Tl content were conducted. The results of X-ray diffraction experiments, SEM and EDX are also presented. AC susceptibility measurements were carried out on a Tl-2212 single crystal under various external magnetic fields applied normal to a-b plane. Measurements of reflectance spectra were also applied to a single crystal of Tl-2223 to investigate the optical anisotropy of Tl-2223.
基金This work was supported by the Ministry of Science and Technology of China(Grant No.NKBRSG-G 1999064602)the National Natural Science Foundation of China(Grant Nos.10174003 and 50377040).
文摘The amplitude-dependent ac susceptibility of high-temperature superconductors is shown to obey some empirical scaling relations. We try to analyze this behavior by extending a dc nonlinear response function of mixed state to the ac cases. The derived equations for critical current and ac susceptibility x(T) agree with the scaling relations of experimental data.
基金supported by the Fundamental Research Funds for the Central Universities of China(Grant No.DL09BB31)the Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education,Lanzhou University,China (Grant No.LZUMMM2010004)+2 种基金the Fundamental Research Funds for the Central Universities of China(Grant No.DL09BB36)the National Natural Science Foundation of China(Grant No.31170518)the Research Fund of Heilongjiang Provincial Education Department(Grant No.12513040)
文摘Ac susceptibility at low temperatures of Pro.75Nao.25MnO3-xFexO3 （0 ≤ x ≤0.30） is investigated. The peak value of the real component of ac susceptibility X＇ at the freezing temperature Tf is suppressed with the increasing frequency. The peak value of X＇ shows a linear relation between Tf and the logarithm of the frequency ω. The normalized slope P = △Tf/Tf△lgco, which is much lower than canonical insulating spin glass systems in which 0.06 ≤ P ≤ 0,08. The peak value of the imaginary component of the ac susceptibility X＂ at Tf for the x= 0, 0.02, 0.30 samples increases with increasing frequency, suggesting a cluster glass ground state with a coexistence of charge-ordered phase and correlated ferromagnetic clusters in spin glass matrix. The peak value ofx＂ at Tf for the x = 0.10 sample decreases with increasing frequency, suggesting a phase separation ground state. The peak value of X＂at Tf for the x = 0.05 sample decreases with increasing frequency for ω ≤52 Hz and increases subsequently till 701 Hz, and then decreases with further increasing frequency for ω ≥ 1501 Hz. This complex behaviour is ascribed to the competition between the effects of large and little ferromagnetic clusters in the sample. The ground state of x = 0.05 sample is a transition state from cluster glass to phase separation.
基金Project supported by Exploratory Research Grants Scheme(ERGS)(5527047)University Putra Malaysia through the Putra Grant(9440100)Ministry of Education Malaysia(MOE)and University Malaysia Terengganu(UMT)
文摘The effects of Nd2O3 nanoparticles addition on microstructure, transport and AC susceptibility properties of YBa2Cu3O7–δ（Y123） superconductors were systematically investigated using X-ray diffraction （XRD）, scanning electron micrograph （SEM）, four point probe measurement and AC spectrometer. It was found that the added samples were predominant by Y-123 phase beside small amount of Y-211 and unreacted Nd2O3secondary phases. All added samples preserved the orthorhombic structure similar to the pure sample and no orthorhombic-to-tetragonal transition occurred. The samples became more porous and their grain size significantly de-creased with addition of Nd2O3. The addition of nano-Nd2O3 disturbed the grain growth of Y123, thus resulting in the degradation of superconducting properties of the samples. The superconducting transition temperature （Tc onset） of samples decreased from 92 K for x=0.0 to 78 K forx=1.0 wt.%, which could be attributable to oxygen vacancy disorder. From AC susceptibility result, the inter- and intra-granular loss peaks became wider and broader with increase of Nd2O3 addition due to the weakening of grains coupling. On the other hand, the inter-granular critical current density,Jcm, was found to increase with Nd2O3 addition and had the highest value at x=0.6, confirming that Nd2O3 nanoparticles acted as pinning centers in Y123 matrix.
文摘In this research two samples of a nominal composition Bi1.6Pb0.4Sr2Ca2Cu3Ox were prepared by the solid state reaction method, using two different routes. Codes A and B are used to refer to the two samples. In preparing sample A, the standard method for calcination was used, while for sample B, the SrCO3 and CaCO3 were calcinated at 1100℃ for 3 h. Calcination was done separately on SrCO3 and CaCO3 in order to eliminate CO2. Then after mixing and grinding, the powder mixtures of Bi2O3, CuO, PbO, SrO and CaO were calcinated at 840℃ for 70 h. Also, the samples (samples C) of nominal compositions Bi1.6Pb0.4Sr2Ca2Cu3Ox+ % x Gd2O3 (% x = 0, 3, 5, 7 and 9) have been synthesized by this method. The XRD and SEM results show that addition of Gd2O3 helps to increase the amount of Bi-2212 phase, while alternative calcination process improves the formation of the Bi-2223 phase. In addition, the AC susceptibility measurements confirm the XRD and SEM results.
基金This work was supported by the National Science Foundation of China under Grant No. 50372052, 50430137, 50588201 the National Basic Research Program of China (973 program), under Grant No. 2007CB616906)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in UniversityAustralian Research Council under Grant No. DP0559872, DP0881739.
文摘Single phase polycrystalline samples Na0.7Co1-xAlxO2 （x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 030） were prepared by solid state reaction. The magnetic properties from 5 K to 300 K have been studied by dc and ac magnetic susceptibility measurements. Samples with lower doping quantity （x = 0, 0.05, 0.10） showed paramagnetic behaviors, but those with higher doping quantity （x=0.20, 0.25, 0.30）showed spin-glass behaviors with a freezing temperature （Tf） of about 13 K.
