In this paper, M-type hexagonal barium ferrite powders are synthesized using the sol-gel method. A dried precursor heated in air is analyzed in the temperature range from 50 to 1200 ℃ using thermo-gravimetric analysi...In this paper, M-type hexagonal barium ferrite powders are synthesized using the sol-gel method. A dried precursor heated in air is analyzed in the temperature range from 50 to 1200 ℃ using thermo-gravimetric analysis and differential scanning calorimetry. The effects of the additives and the cacinating temperature on the magnetic properties are investigated, and the results show that single-phase barium ferrite powders can be formed. After heat-treating at 950 ℃ for 4h with 3 wt% additive, the coercivity and saturation magnetization are found to be 440 Oe and 57.9 emu/g, respectively.展开更多
Single-phase VO_(2) thin films are sputtering deposited on BK7 substrates,and sharp insulator-to-metal phase transition is obtained with a resistivity change of four orders of magnitude.Terahertz(THz)pump-probe measur...Single-phase VO_(2) thin films are sputtering deposited on BK7 substrates,and sharp insulator-to-metal phase transition is obtained with a resistivity change of four orders of magnitude.Terahertz(THz)pump-probe measurements reveal that by illuminating the films with a low pumping power of 143μJ/cm^(2),VO_(2) films exhibit an ultrafast optical switching to THz transmission within 8 ps.Furthermore,the THz switching ratio reaches over 80%in a wide frequency range from 0.3 to 2.5 THz.All these outstanding features indicate a strong potential of VO_(2) films for broadband terahertz wave switching and modulation applications.展开更多
In order to linearize a spin-valve giant magnetoresistance head,the exchanges layer sputtered at fringe area or a permanent magnet layer longitudinal biasing for domain stabilization based on a physical calculated mod...In order to linearize a spin-valve giant magnetoresistance head,the exchanges layer sputtered at fringe area or a permanent magnet layer longitudinal biasing for domain stabilization based on a physical calculated model may be considered.The correlations between the head performance characteristic and head geometric parameters have been simulated by putting the head on a suitable front-end electric circuit.The simulative results show that the optimal sensing current is from 10 to 40mA and the linear geometric parameteres for gap width are at the range of G_(1)+G_(2)≤0.5μm.展开更多
The effects of grain size and magnetic domain state on the power loss(from low to high induction conditions)and permeability characteristics of NiZn ferrites are investigated.It is found that under relatively low indu...The effects of grain size and magnetic domain state on the power loss(from low to high induction conditions)and permeability characteristics of NiZn ferrites are investigated.It is found that under relatively low induction conditions(B_(m)<50 mT),a NiZn ferrite with a dense and monodomain microstructure obtains the lowest power loss.However,a NiZn ferrite with a larger average grain size displays a lower power loss under high induction conditions,and the influence of domain state on power loss is inconspicuous.Extremely large grain size and closed pores also lead to a poor frequency stability of permeability.Thus,synthetically considering the power loss and permeability characteristics,a NiZn ferrite with an even and large average grain size also has few closed pores and is the best choice for use under high induction conditions.展开更多
It is believed that the ultrafast demagnetization process in ferromagnetic film is intrinsically a thermal effect,which is induced by ultrafast laser pulses.We present experimental evidence that such ultrafast demagne...It is believed that the ultrafast demagnetization process in ferromagnetic film is intrinsically a thermal effect,which is induced by ultrafast laser pulses.We present experimental evidence that such ultrafast demagnetization of the NiFe thin film can radiate electromagnetic waves in the terahertz range.We also demonstrate that the magnitude of the terahertz electromagnetic pulse emitted from ferromagnetic films alter pulsed laser excitation can be tuned by the Gilbert damping factor α,which is conventionally used to describe damping of GHz precession motion of magnetization.Different damping factors are obtained by varying the normal metal film adjacent to the magnetic film via spin pumping.The measured radiated electric field in the far field is found to be proportional to the Gilbert damping factor.展开更多
A systematic study of the charge transport and electrical properties in poly(3-hexylthiophene) (P3HT) polymer layers is performed.We demonstrate that the temperature-dependent current-voltage J (V,T) characteristics o...A systematic study of the charge transport and electrical properties in poly(3-hexylthiophene) (P3HT) polymer layers is performed.We demonstrate that the temperature-dependent current-voltage J (V,T) characteristics of hole-only devices based on P3HT can be accurately described using the recently introduced extended Gaussian disorder model (EGDM).A particular numerical method adopting the uneven discretization and Newton iteration method is used to solve the coupled equations describing the space-charge limited (SCL) current in conjugated polymers.For the polymer studied,we find the width of the density of states σ =0.1 eV and the lattice constant a =1.15nm.Based on the numerical method and EGDM,we further calculate and analyze some important electrical properties for P3HT in detail,including the variation of current-voltage characteristics with the boundary carrier density and the distribution of charge-carrier density and electric field with the distance from interface.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2007CB310407)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.61021061)+1 种基金the National Natural Youth Fund of China(Grant No.61001025)National Programs for Science and Technology Development of Guangdong Province,China(Grant No.2010B090400314)
文摘In this paper, M-type hexagonal barium ferrite powders are synthesized using the sol-gel method. A dried precursor heated in air is analyzed in the temperature range from 50 to 1200 ℃ using thermo-gravimetric analysis and differential scanning calorimetry. The effects of the additives and the cacinating temperature on the magnetic properties are investigated, and the results show that single-phase barium ferrite powders can be formed. After heat-treating at 950 ℃ for 4h with 3 wt% additive, the coercivity and saturation magnetization are found to be 440 Oe and 57.9 emu/g, respectively.
基金Supported by the National Nature Science Foundation of China under Grant Nos 61131005 and 61021061Keygrant Project of the Ministry of Education of China(No 313013)+4 种基金the New Century Excellent Talent Foundation(No NCET-11-0068)Sichuan Youth S&T Foundation(No 2011JQ0001)Specialized Research Fund for the Doctoral Program of Higher Education(No 20110185130002)the Fundamental Research Funds for the Central Universities(No ZYGX2010J034)the CAEP THz Science and Technology Foundation(No CAEPTHZ201207).
文摘Single-phase VO_(2) thin films are sputtering deposited on BK7 substrates,and sharp insulator-to-metal phase transition is obtained with a resistivity change of four orders of magnitude.Terahertz(THz)pump-probe measurements reveal that by illuminating the films with a low pumping power of 143μJ/cm^(2),VO_(2) films exhibit an ultrafast optical switching to THz transmission within 8 ps.Furthermore,the THz switching ratio reaches over 80%in a wide frequency range from 0.3 to 2.5 THz.All these outstanding features indicate a strong potential of VO_(2) films for broadband terahertz wave switching and modulation applications.
文摘In order to linearize a spin-valve giant magnetoresistance head,the exchanges layer sputtered at fringe area or a permanent magnet layer longitudinal biasing for domain stabilization based on a physical calculated model may be considered.The correlations between the head performance characteristic and head geometric parameters have been simulated by putting the head on a suitable front-end electric circuit.The simulative results show that the optimal sensing current is from 10 to 40mA and the linear geometric parameteres for gap width are at the range of G_(1)+G_(2)≤0.5μm.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61171047,51072029 and 61021061the National High-Tech Research and Development Program of China under Grant No 2009AA03Z414.
文摘The effects of grain size and magnetic domain state on the power loss(from low to high induction conditions)and permeability characteristics of NiZn ferrites are investigated.It is found that under relatively low induction conditions(B_(m)<50 mT),a NiZn ferrite with a dense and monodomain microstructure obtains the lowest power loss.However,a NiZn ferrite with a larger average grain size displays a lower power loss under high induction conditions,and the influence of domain state on power loss is inconspicuous.Extremely large grain size and closed pores also lead to a poor frequency stability of permeability.Thus,synthetically considering the power loss and permeability characteristics,a NiZn ferrite with an even and large average grain size also has few closed pores and is the best choice for use under high induction conditions.
基金Supported by the Fund for Innovative Research Groups of the National Natural Science Foundation of China(61021061)the National Basic Research Program of China under Grant No 2012CB933104+4 种基金the Youth Fund of the National Natural Science Foundation of China(No 61001025)the Scientific Fund for College(No ZYGX2011X006)the Fund of Guangdong Province for Research and Industrialization(No 2010B090400314)the Opening Fund of State Key Laboratory(KFJJ201102)the Fund of Key Laboratory of Education Ministry.
文摘It is believed that the ultrafast demagnetization process in ferromagnetic film is intrinsically a thermal effect,which is induced by ultrafast laser pulses.We present experimental evidence that such ultrafast demagnetization of the NiFe thin film can radiate electromagnetic waves in the terahertz range.We also demonstrate that the magnitude of the terahertz electromagnetic pulse emitted from ferromagnetic films alter pulsed laser excitation can be tuned by the Gilbert damping factor α,which is conventionally used to describe damping of GHz precession motion of magnetization.Different damping factors are obtained by varying the normal metal film adjacent to the magnetic film via spin pumping.The measured radiated electric field in the far field is found to be proportional to the Gilbert damping factor.
基金Supported by the National Basic Research Program of China under Grant No 2007CB310407the Foundation for Innovative Research Groups of the National Natural Science Foundation of China under Grant No 61021061+1 种基金the National Natural Science Foundation of China under Grant Nos 50972023,61001025,and 61071028the International S&T Cooperation Program of China under Grant No 2006DFA53410.
文摘A systematic study of the charge transport and electrical properties in poly(3-hexylthiophene) (P3HT) polymer layers is performed.We demonstrate that the temperature-dependent current-voltage J (V,T) characteristics of hole-only devices based on P3HT can be accurately described using the recently introduced extended Gaussian disorder model (EGDM).A particular numerical method adopting the uneven discretization and Newton iteration method is used to solve the coupled equations describing the space-charge limited (SCL) current in conjugated polymers.For the polymer studied,we find the width of the density of states σ =0.1 eV and the lattice constant a =1.15nm.Based on the numerical method and EGDM,we further calculate and analyze some important electrical properties for P3HT in detail,including the variation of current-voltage characteristics with the boundary carrier density and the distribution of charge-carrier density and electric field with the distance from interface.
