By finely controlling the deposition parameters in the pulsed electron deposition process, granular La 2/3 Ca 1/3 MnO 3 （LCMO） film was grown on silicon substrates. The substrate temperature, ambient pressure in the...By finely controlling the deposition parameters in the pulsed electron deposition process, granular La 2/3 Ca 1/3 MnO 3 （LCMO） film was grown on silicon substrates. The substrate temperature, ambient pressure in the deposition chamber and acceleration potential for the electron beam were all found to affect the grain size of the film, resulting in different morphologies of the samples. Transport properties of the obtained granular films, especially the magnetoresistance （MR）, were studied. Prominent low-field MR was observed in all samples, indicating the forming of grain boundaries in the sample. The low-field MR show great sensitive to the morphology evolution, which reaches the highest value of about 40% for the sample with the grain size of about 250 nm. More interestingly, positive-MR （p-MR） was also detected above 300 K when low magnetic field applying, whereas it disappeared with higher magnetic field applied up to 1.5 and 2 Tesla. Instead of the spin- polarized tunneling process being commonly regarded as a responsible reason, lattice mismatch between LCMO film and silicon substrate appears to be the origin of the p-MR展开更多
Prx（Co40Ag60）100-x （x=0, 0.5, 1, 1.5, 2, 3） granular films have been prepared by DC magneto controlled sputtering method. The XRD data indicated that Pr element favors the （111） plane preferential orientation. M...Prx（Co40Ag60）100-x （x=0, 0.5, 1, 1.5, 2, 3） granular films have been prepared by DC magneto controlled sputtering method. The XRD data indicated that Pr element favors the （111） plane preferential orientation. Magnetic measurements indicate that the average size of magnetic particles decreases as Pr content increases. For relatively low addition of Pr to CoAg granular films, Pr element can enhance GMR value and a peak value of about -14.3% is obtained at x=1.展开更多
We present a detailed study on the magnetic coercivity of Co/CoO-MgO core-shell systems, which exhibits a large exchange bias due to an increase of the uncompensated spin density at the interface between the CoO shell...We present a detailed study on the magnetic coercivity of Co/CoO-MgO core-shell systems, which exhibits a large exchange bias due to an increase of the uncompensated spin density at the interface between the CoO shell and the metallic Co core by replacing Co by Mg within the CoO shell. We find a large magnetic coercivity of 7120 Oe around the electrical percolation threshold of the Co/CoO core/shell particles, while samples with a smaller or larger Co metal volume fraction show a considerably smaller coercivity. Thus, this study may lead to a route to improving the magnetic properties of artificial magnetic material in view of potential applications.展开更多
Cux（Cu2O）1-x（0.09 x 1.00） granular films with thickness about 280 nm have been fabricated by direct current reactive magnetron sputtering. The atomic ratio x can be controlled by the oxygen flow rate during Cux（C...Cux（Cu2O）1-x（0.09 x 1.00） granular films with thickness about 280 nm have been fabricated by direct current reactive magnetron sputtering. The atomic ratio x can be controlled by the oxygen flow rate during Cux（Cu2O）1-x deposition. Room-temperature ferromagnetism（FM） is found in all of the samples. The saturated magnetization increases at first and then decreases with the decrease of x. The photoluminescence spectra show that the magnetization is closely correlated with the Cu vacancies in the Cux（Cu2O）1-x granular films. Fundamentally, the FM could be understood by the Stoner model based on the charge transfer mechanism. These results may provide solid evidence and physical insights on the origin of FM in the Cu2O-based oxides diluted magnetic semiconductors, especially for systems without intentional magnetic atom doping.展开更多
The effect of the volume fraction of ferromagnetic metal （x） in （Ni75Fe25）x（ZnO）1-x nanogranular thin films on microstructural, soft-magnetic, and high-frequency properties was investigated. Good soft-magnetic p...The effect of the volume fraction of ferromagnetic metal （x） in （Ni75Fe25）x（ZnO）1-x nanogranular thin films on microstructural, soft-magnetic, and high-frequency properties was investigated. Good soft-magnetic properties were obtained in a broad x range, with 0.55 〈 x 〈 0.82. High resolution transmission electron microscopy （HRTEM） observations reveal that the grain size of the samples is lower than 14 nm, and that it decreases with decreasing x. Of special interest, our investigation of the permeability spectra indicates that these films exhibit an adjustable frequency linewidth of resonance peak, dependant upon changing x. Correspondingly, large and adjustable damping coefficients （aeff） from 0.023 to 0.043 were achieved by decreasing x from 0.82 to 0.55. Combined with the HRTEM results, the variation of αeff with x was analyzed in detail.展开更多
Nanometer ferromagnetic metal-semiconductor matrix Fe-In2O3 granular films are fabricated by the radio frequency sputtering. Magnetic properties and the giant magnetoresistance (GMR) effect of Fex(In2O3)1-x granular f...Nanometer ferromagnetic metal-semiconductor matrix Fe-In2O3 granular films are fabricated by the radio frequency sputtering. Magnetic properties and the giant magnetoresistance (GMR) effect of Fex(In2O3)1-x granular film samples are studied. The result shows that the magnetoresistance (MR) ratio value of the granular film samples with Fe volume fraction x = 35% is 4.5% at room temperature. The temperature dependence (r = 1.5-300 K) of the MR ratio value of Fe0.35(In2O3)0.65 granular films shows that value below 10 K increases rapidly with the decrease of the temperature, and when T = 2 K, value is 85%. Through the study of the dependence of low field susceptibility on temperature and the hysteresis loops at different temperatures, it has been found that, when the temperature decreases to a critical point TP = 10 K, the change of the structure in Fe0.35(In2O3)0.65 granular films results in the transformation of state from ferromagnetic to spin-glass-like. The remarkable increase of the MR ratio value展开更多
Amorphous CoxC1-x granular films were prepared on n-Si(100) substrate by dc magnetron sputtering.The effects of Co concentration,film thickness and annealing temperature on the magnetic properties and magnetoresistanc...Amorphous CoxC1-x granular films were prepared on n-Si(100) substrate by dc magnetron sputtering.The effects of Co concentration,film thickness and annealing temperature on the magnetic properties and magnetoresistance(MR) were investigated.After annealing at 500°C for 0.5 hour,the Co(002) peak of the CoxC1-x(x>2.5 at.%) films was observed,but cracks appeared in the films.Saturation magnetization Ms increased steadily with the increase of Co concentration from 2.5 at.% to 50 at.% and also increased with annealing temperature from room temperature to 400°C.The coercivity of CoxC1-x films was less than 180 Oe.The as-deposited Co2.5C97.5 granular films with 80 nm thickness showed a highly positive MR,up to 15.5% at a magnetic field of 0.8 T,observed at T=300 K when the external magnetic field was perpendicular to the film surface.With increasing film thickness and annealing temperature,the value of MR was found to decrease gradually and changed from positive to negative.The MR effect of the CoxC1-x granular films can be explained by p-n heterojunction theory and interface scattering effect.展开更多
In this paper,we present a review of electron transport properties of magnetic granular films.Magnetic granular films are nanocomposite materials which consist of magnetic nanoparticles embedded in a nonmagnetic matri...In this paper,we present a review of electron transport properties of magnetic granular films.Magnetic granular films are nanocomposite materials which consist of magnetic nanoparticles embedded in a nonmagnetic matrix or assembling of magnetic nanoparticles.According to the style of the nonmagnetic matrix,microstructure and the electron transport mechanism of the films,the magnetic granular films were divided into three groups:(1) magnetic metal-metal granular films,(2) magnetic metal-insulator granular films and(3) magnetic nanocluster-assembled granular films.Moreover,we also systematically review the magnetic properties,transport properties and magnetoresistance effect of size-monodispersed Co and Fe nanocluster-assembled films.展开更多
The giant magneto-optical Faraday effect of nanometer ferromagnetic metal-semiconductor matrix Fe-In2O3 granular films prepared by the radio frequency sputtering are studied. The result shows that the Faraday rotation...The giant magneto-optical Faraday effect of nanometer ferromagnetic metal-semiconductor matrix Fe-In2O3 granular films prepared by the radio frequency sputtering are studied. The result shows that the Faraday rotation angle θF value of the granular film samples with Fe volume fraction x = 35% is of the order of 105(°)/cm at room temperature. Temperature dependence of the Faraday rotation angle θF of Fe0.35(In2O3)0.65 granular films shows that θF value below 10 K increases rapidly with the decrease of the temperature, and when T = 4.2 K, θF value is 106(°)/cm. Through the study of the dependence of low field susceptibility on temperature and the hysteresis loops at different temperatures, it has been found that when the temperature decreases to a critical point TP = 10 K, the transformation of state from ferro- magnetic to spin-glass-like occurs in Fe0.35(In2O3)0.65 granular films. The remarkable increase of the Faraday rotation angle θF value of Fe0.35(In2O3)0.65 granular films below 10 K seems to arise from the sp-d exchange interaction of the granular film samples in the spin-glass-like state.展开更多
We review the recently discovered tunnel-type giant magnetoresistance (GMR) in ferromagnetic metal-insulator granular thin films, which is the magnetoresistance (MR) associated with the spin-dependent tunneling betwee...We review the recently discovered tunnel-type giant magnetoresistance (GMR) in ferromagnetic metal-insulator granular thin films, which is the magnetoresistance (MR) associated with the spin-dependent tunneling between two ferromagnetic metal particles. The theoretical and experimental results including electrical resistivity, magnetoresistance and their temperature dependence are described. Limitations to the applications of the ferromagnetic metal-insulator granular films are also discussed. Additionally, a brief survey of another two magnetic properties, high- frequency property and giant Hall effect (GHE) associated strongly with the granular structures is also presented.展开更多
Fefv(SiO2)1-fv granular films were fabricated by rf sputtering (fv represents the Fe volume fraction). The mi-crostructure, magnetic properties as well as the tunneling magnetoresistance effect (TMR) were systematical...Fefv(SiO2)1-fv granular films were fabricated by rf sputtering (fv represents the Fe volume fraction). The mi-crostructure, magnetic properties as well as the tunneling magnetoresistance effect (TMR) were systematically studied. It was found that the maximum TMR ratio is about -3.3% at fv = 0.33. Under the same condition, a series of (Fe100-x Cox)0.33(SiO2)0.67 were prepared. TMR value reaches -4.5% at x=53, while the microstructure of the film still keeps as that of Fe0.33(SiO2)0.67. The higher TMR ratio is contributed to the elevating of the spin polarization of particles. This is consistent with Inoue’s theory.展开更多
A series of CoxAg1-x nanostructured granular films have been prepared by ion beam sputtering and annealed at 100, 250, 400, 5001. The optical constants, the complex dielectric func-tion and magneto-optical Kerr parame...A series of CoxAg1-x nanostructured granular films have been prepared by ion beam sputtering and annealed at 100, 250, 400, 5001. The optical constants, the complex dielectric func-tion and magneto-optical Kerr parameters were measured at room temperature. For the samples hav-ing low Co compositions, the strong Kerr effect enhancement is observed around the Ag plasma edge. With an increase in annealing temperature, the resonance-like peaks appear in the Kerr rotation, and the peak positions are shifted toward the low photon energy region. From the analysis of the numerical calculations, it is concluded that the magneto-optical Kerr effect enhancement (MOKE) is due to the presence of the steep plasma edge.展开更多
From the point of view of application in the microwave band,the theoretic and experimental researches of nanostructural magnetic films were carried out. Micromagnetic structure of the nano-magnetic film was simulated ...From the point of view of application in the microwave band,the theoretic and experimental researches of nanostructural magnetic films were carried out. Micromagnetic structure of the nano-magnetic film was simulated by the finite element method. The typical micromagnetic was obtained. Corresponding experiments were also done aiming at the Co40Fe40B20-SiO2 nano-granular films. The results show that the characteristics of nano-magnetic film correspond with the micromagnetic ripple theory. The microwave permeability of nano-magnetic films deduces and well fits the Landau-Lifshitz-Gilbert(LLG) equation. The films present large microwave permeability and high resonant frequency(μ′ and μ″ at 2 GHz are about 100 and 40 respectively and the resonant frequency is about 2.8 GHz). The additional peak of μ″ originated from perpendicular anisotropy and micromagnetic ripple structure can be suppressed by the annealing process. Thus,the microwave complex permeability spectra of these nano-magnetic films can be tailored for different applications.展开更多
Polycrystalline silicon thin films were prepared by RTCVD (rapid thermal chemica l vapor deposition) method on several substrates such as SSP (silicon sheet from powder) ribbon, poly-Si wafer and mono-Si wafer. Intra-...Polycrystalline silicon thin films were prepared by RTCVD (rapid thermal chemica l vapor deposition) method on several substrates such as SSP (silicon sheet from powder) ribbon, poly-Si wafer and mono-Si wafer. Intra-granular defects such as stacking faults, twins and microstructure defects were investigated on thin fil ms by scan electron microscopy (SEM) technique.展开更多
This paper reports that single-layer and graded Au-TiO2 granular composite films with Au atom content 15%- 66% were prepared by using reactive co-sputtering technique. The third-order optical nonlinearity of single-la...This paper reports that single-layer and graded Au-TiO2 granular composite films with Au atom content 15%- 66% were prepared by using reactive co-sputtering technique. The third-order optical nonlinearity of single-layer and graded composite films was investigated by using s- and p-polarized Z-scans in femtosecond time scale. The nonlinear absorption coefficient βeff of single-layer Au-TiO2 films is measured to be -2.3×10^3-0.76×10^3 cm/GW with Au atom content 15%-66%. The βeff value of the 10-layer Au-TiO2 graded film is enhanced to be -2.1×10^4cm/GW calculated from p-polarized Z-scans, which is about ten times the maximum βeff of single-layer films. Broadened response in the wavelength region 730-860 nm of the enhanced optical nonlinearity of graded Au-TiO2 composite films was also investigated.展开更多
基金Funded by the National Natural Science Foundation of China(No.10875107)the Aeronautical Science Foundation(No.2010ZF55013)+1 种基金the Basic and Advanced Technology Program of Henan Province (No.112300410229)the Foundation for University Young Key Teacher by Henan Province (No. 2010GGJS-146)
文摘By finely controlling the deposition parameters in the pulsed electron deposition process, granular La 2/3 Ca 1/3 MnO 3 （LCMO） film was grown on silicon substrates. The substrate temperature, ambient pressure in the deposition chamber and acceleration potential for the electron beam were all found to affect the grain size of the film, resulting in different morphologies of the samples. Transport properties of the obtained granular films, especially the magnetoresistance （MR）, were studied. Prominent low-field MR was observed in all samples, indicating the forming of grain boundaries in the sample. The low-field MR show great sensitive to the morphology evolution, which reaches the highest value of about 40% for the sample with the grain size of about 250 nm. More interestingly, positive-MR （p-MR） was also detected above 300 K when low magnetic field applying, whereas it disappeared with higher magnetic field applied up to 1.5 and 2 Tesla. Instead of the spin- polarized tunneling process being commonly regarded as a responsible reason, lattice mismatch between LCMO film and silicon substrate appears to be the origin of the p-MR
基金supported by the National Natural Science Foundation of China(Grant No:10274018)the Foundation of Hebei Provincial Education Department(Grant No:002013)the Key Foundation of Hebei Normal University(Grant No:120203).
基金Funded by the National Natural Science Foundation of Guangxi and Guangxi Key Laboratory of Information Materials Foundation (No.0575093&0710908-11-Z)
文摘Prx（Co40Ag60）100-x （x=0, 0.5, 1, 1.5, 2, 3） granular films have been prepared by DC magneto controlled sputtering method. The XRD data indicated that Pr element favors the （111） plane preferential orientation. Magnetic measurements indicate that the average size of magnetic particles decreases as Pr content increases. For relatively low addition of Pr to CoAg granular films, Pr element can enhance GMR value and a peak value of about -14.3% is obtained at x=1.
基金supported by the National Basic Research Program of China(Grant No.2012CB932304)the National Natural Science Foundation of China(Grant Nos.U1232210,91122035,11174124,and 11374137)+1 种基金the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.14KJB140003)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘We present a detailed study on the magnetic coercivity of Co/CoO-MgO core-shell systems, which exhibits a large exchange bias due to an increase of the uncompensated spin density at the interface between the CoO shell and the metallic Co core by replacing Co by Mg within the CoO shell. We find a large magnetic coercivity of 7120 Oe around the electrical percolation threshold of the Co/CoO core/shell particles, while samples with a smaller or larger Co metal volume fraction show a considerably smaller coercivity. Thus, this study may lead to a route to improving the magnetic properties of artificial magnetic material in view of potential applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11104148,51101088,and 51171082)the Tianjin Natural Science Foundation,China(Grant Nos.14JCZDJC37700 and 13JCQNJC02800)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20110031110034)the Fundamental Research Funds for the Central Universities,China
文摘Cux（Cu2O）1-x（0.09 x 1.00） granular films with thickness about 280 nm have been fabricated by direct current reactive magnetron sputtering. The atomic ratio x can be controlled by the oxygen flow rate during Cux（Cu2O）1-x deposition. Room-temperature ferromagnetism（FM） is found in all of the samples. The saturated magnetization increases at first and then decreases with the decrease of x. The photoluminescence spectra show that the magnetization is closely correlated with the Cu vacancies in the Cux（Cu2O）1-x granular films. Fundamentally, the FM could be understood by the Stoner model based on the charge transfer mechanism. These results may provide solid evidence and physical insights on the origin of FM in the Cu2O-based oxides diluted magnetic semiconductors, especially for systems without intentional magnetic atom doping.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.50901050 and 51101079)
文摘The effect of the volume fraction of ferromagnetic metal （x） in （Ni75Fe25）x（ZnO）1-x nanogranular thin films on microstructural, soft-magnetic, and high-frequency properties was investigated. Good soft-magnetic properties were obtained in a broad x range, with 0.55 〈 x 〈 0.82. High resolution transmission electron microscopy （HRTEM） observations reveal that the grain size of the samples is lower than 14 nm, and that it decreases with decreasing x. Of special interest, our investigation of the permeability spectra indicates that these films exhibit an adjustable frequency linewidth of resonance peak, dependant upon changing x. Correspondingly, large and adjustable damping coefficients （aeff） from 0.023 to 0.043 were achieved by decreasing x from 0.82 to 0.55. Combined with the HRTEM results, the variation of αeff with x was analyzed in detail.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 59981004).
文摘Nanometer ferromagnetic metal-semiconductor matrix Fe-In2O3 granular films are fabricated by the radio frequency sputtering. Magnetic properties and the giant magnetoresistance (GMR) effect of Fex(In2O3)1-x granular film samples are studied. The result shows that the magnetoresistance (MR) ratio value of the granular film samples with Fe volume fraction x = 35% is 4.5% at room temperature. The temperature dependence (r = 1.5-300 K) of the MR ratio value of Fe0.35(In2O3)0.65 granular films shows that value below 10 K increases rapidly with the decrease of the temperature, and when T = 2 K, value is 85%. Through the study of the dependence of low field susceptibility on temperature and the hysteresis loops at different temperatures, it has been found that, when the temperature decreases to a critical point TP = 10 K, the change of the structure in Fe0.35(In2O3)0.65 granular films results in the transformation of state from ferromagnetic to spin-glass-like. The remarkable increase of the MR ratio value
基金supported by the National Natural Science Foundation of China (Grant No. U0734001)the Fundamental Research Funds for the Central Universities, South China University Of Technology (Grant No. 2009ZM0247)
文摘Amorphous CoxC1-x granular films were prepared on n-Si(100) substrate by dc magnetron sputtering.The effects of Co concentration,film thickness and annealing temperature on the magnetic properties and magnetoresistance(MR) were investigated.After annealing at 500°C for 0.5 hour,the Co(002) peak of the CoxC1-x(x>2.5 at.%) films was observed,but cracks appeared in the films.Saturation magnetization Ms increased steadily with the increase of Co concentration from 2.5 at.% to 50 at.% and also increased with annealing temperature from room temperature to 400°C.The coercivity of CoxC1-x films was less than 180 Oe.The as-deposited Co2.5C97.5 granular films with 80 nm thickness showed a highly positive MR,up to 15.5% at a magnetic field of 0.8 T,observed at T=300 K when the external magnetic field was perpendicular to the film surface.With increasing film thickness and annealing temperature,the value of MR was found to decrease gradually and changed from positive to negative.The MR effect of the CoxC1-x granular films can be explained by p-n heterojunction theory and interface scattering effect.
基金supported by the National Basic Research Program of China (Grant No. 2012CB933103)the National Science Fund for Distinguished Young Scholars (Grant No. 50825101)the National Natural Science Foundation of China (Grant Nos. 50971108 and 51171158)
文摘In this paper,we present a review of electron transport properties of magnetic granular films.Magnetic granular films are nanocomposite materials which consist of magnetic nanoparticles embedded in a nonmagnetic matrix or assembling of magnetic nanoparticles.According to the style of the nonmagnetic matrix,microstructure and the electron transport mechanism of the films,the magnetic granular films were divided into three groups:(1) magnetic metal-metal granular films,(2) magnetic metal-insulator granular films and(3) magnetic nanocluster-assembled granular films.Moreover,we also systematically review the magnetic properties,transport properties and magnetoresistance effect of size-monodispersed Co and Fe nanocluster-assembled films.
基金the National Natural Science Foundation of China (Grant No. 10674082)
文摘The giant magneto-optical Faraday effect of nanometer ferromagnetic metal-semiconductor matrix Fe-In2O3 granular films prepared by the radio frequency sputtering are studied. The result shows that the Faraday rotation angle θF value of the granular film samples with Fe volume fraction x = 35% is of the order of 105(°)/cm at room temperature. Temperature dependence of the Faraday rotation angle θF of Fe0.35(In2O3)0.65 granular films shows that θF value below 10 K increases rapidly with the decrease of the temperature, and when T = 4.2 K, θF value is 106(°)/cm. Through the study of the dependence of low field susceptibility on temperature and the hysteresis loops at different temperatures, it has been found that when the temperature decreases to a critical point TP = 10 K, the transformation of state from ferro- magnetic to spin-glass-like occurs in Fe0.35(In2O3)0.65 granular films. The remarkable increase of the Faraday rotation angle θF value of Fe0.35(In2O3)0.65 granular films below 10 K seems to arise from the sp-d exchange interaction of the granular film samples in the spin-glass-like state.
基金the National NaturalScience Foundation of China (Grant No. 59801006) the Key Teacher Supporting Project (Grant No. G00032) +1 种基金and the Starting Foundation of Returned Researchers of the National Education Committee and Tianjin Youth Science Foundatio
文摘We review the recently discovered tunnel-type giant magnetoresistance (GMR) in ferromagnetic metal-insulator granular thin films, which is the magnetoresistance (MR) associated with the spin-dependent tunneling between two ferromagnetic metal particles. The theoretical and experimental results including electrical resistivity, magnetoresistance and their temperature dependence are described. Limitations to the applications of the ferromagnetic metal-insulator granular films are also discussed. Additionally, a brief survey of another two magnetic properties, high- frequency property and giant Hall effect (GHE) associated strongly with the granular structures is also presented.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 59971023).
文摘Fefv(SiO2)1-fv granular films were fabricated by rf sputtering (fv represents the Fe volume fraction). The mi-crostructure, magnetic properties as well as the tunneling magnetoresistance effect (TMR) were systematically studied. It was found that the maximum TMR ratio is about -3.3% at fv = 0.33. Under the same condition, a series of (Fe100-x Cox)0.33(SiO2)0.67 were prepared. TMR value reaches -4.5% at x=53, while the microstructure of the film still keeps as that of Fe0.33(SiO2)0.67. The higher TMR ratio is contributed to the elevating of the spin polarization of particles. This is consistent with Inoue’s theory.
文摘A series of CoxAg1-x nanostructured granular films have been prepared by ion beam sputtering and annealed at 100, 250, 400, 5001. The optical constants, the complex dielectric func-tion and magneto-optical Kerr parameters were measured at room temperature. For the samples hav-ing low Co compositions, the strong Kerr effect enhancement is observed around the Ag plasma edge. With an increase in annealing temperature, the resonance-like peaks appear in the Kerr rotation, and the peak positions are shifted toward the low photon energy region. From the analysis of the numerical calculations, it is concluded that the magneto-optical Kerr effect enhancement (MOKE) is due to the presence of the steep plasma edge.
基金Project (60771028) supported by the National Natural Science Foundation of China
文摘From the point of view of application in the microwave band,the theoretic and experimental researches of nanostructural magnetic films were carried out. Micromagnetic structure of the nano-magnetic film was simulated by the finite element method. The typical micromagnetic was obtained. Corresponding experiments were also done aiming at the Co40Fe40B20-SiO2 nano-granular films. The results show that the characteristics of nano-magnetic film correspond with the micromagnetic ripple theory. The microwave permeability of nano-magnetic films deduces and well fits the Landau-Lifshitz-Gilbert(LLG) equation. The films present large microwave permeability and high resonant frequency(μ′ and μ″ at 2 GHz are about 100 and 40 respectively and the resonant frequency is about 2.8 GHz). The additional peak of μ″ originated from perpendicular anisotropy and micromagnetic ripple structure can be suppressed by the annealing process. Thus,the microwave complex permeability spectra of these nano-magnetic films can be tailored for different applications.
基金This work was supported by the Chinese Academy of Sciences within"The Hundred Talent Projecr"(99-019-122288)National High Technical Research and Development Programme of China(No.2001AA513060)+1 种基金the 10th Five-Year Plan of Guangdong Province(A1100501)the National Natural Science Fundation of China(No.50376067).
文摘Polycrystalline silicon thin films were prepared by RTCVD (rapid thermal chemica l vapor deposition) method on several substrates such as SSP (silicon sheet from powder) ribbon, poly-Si wafer and mono-Si wafer. Intra-granular defects such as stacking faults, twins and microstructure defects were investigated on thin fil ms by scan electron microscopy (SEM) technique.
基金Project supported by the National Natural Science Foundation of China (Grant No 10474075)
文摘This paper reports that single-layer and graded Au-TiO2 granular composite films with Au atom content 15%- 66% were prepared by using reactive co-sputtering technique. The third-order optical nonlinearity of single-layer and graded composite films was investigated by using s- and p-polarized Z-scans in femtosecond time scale. The nonlinear absorption coefficient βeff of single-layer Au-TiO2 films is measured to be -2.3×10^3-0.76×10^3 cm/GW with Au atom content 15%-66%. The βeff value of the 10-layer Au-TiO2 graded film is enhanced to be -2.1×10^4cm/GW calculated from p-polarized Z-scans, which is about ten times the maximum βeff of single-layer films. Broadened response in the wavelength region 730-860 nm of the enhanced optical nonlinearity of graded Au-TiO2 composite films was also investigated.
