The combination of ferromagnetic metal(FM)and semiconductor(SC)for spin injection was studied and demonstrated with FM-SC-FM junction.The semiconductor was chosen to be doped Indium-Tin-Oxide(ITO).Both ITO single-laye...The combination of ferromagnetic metal(FM)and semiconductor(SC)for spin injection was studied and demonstrated with FM-SC-FM junction.The semiconductor was chosen to be doped Indium-Tin-Oxide(ITO).Both ITO single-layer film and CoFe-ITO-CoFe junction were sputtering deposited.The ITO single-layer film was n-type with a small resistance of about 100Ω/Square.I-V curves and Magnetoresistance(MR)effect of the CoFe-ITO-CoFe junction were measured at room temperature and 77 K.Results show that the CoFe forms an ohmic contact to ITO film.But at low temperature,the I-V curves show a Schottky-like characteristic,which is strongly affect by applied magnetic field.The MR effect was measured to be 1%at 77 K,which indicates a spin injection into semiconductor to be realized in this sandwich junction.展开更多
The magnetic reversal mechanism has been determined within a micromagnetic model reliably for a two-phased magnetic nanosystem, with the formulae for nucleation fields derived analytically. It is found that the nuclea...The magnetic reversal mechanism has been determined within a micromagnetic model reliably for a two-phased magnetic nanosystem, with the formulae for nucleation fields derived analytically. It is found that the nucleation field HN decreases uni- formly as the size of the soft phase Ls increases whereas it increases with the size of the hard phase Lh. The analysis shows that whilst the effect of Lh could be ignored in most cases, where the nucleation field is dominated by the Ls and the calculation could be significantly simplified, the overly simple inverse square law between Hu and the soft layer thickness Ls adopted by the previous researchers is not a good approximation. While nucleation is the beginning of the magnetic reversal, pinning is the dominant coercivity mechanism in both two-phased and single-phased magnetic materials, where the crystalline defects exist. Comparison with the experimental data confirms this conclusion, indicating that Brown＇s paradox results from the much lower effective anisotropy in both single-phased and composite materials, as speculated in the literature.展开更多
The microstructure and magnetic properties of cobalt ferrite thin films deposited by the sputtering method on an Fe3o4 un- der-layer were investigated at different post-annealing temperatures. Results show that the Fe...The microstructure and magnetic properties of cobalt ferrite thin films deposited by the sputtering method on an Fe3o4 un- der-layer were investigated at different post-annealing temperatures. Results show that the Fe3o4 under-layer can accelerate the grain growth of cobalt ferrite films due to the phase transformation of the Fe3o4 under-layer at about 400℃-500℃. By intro- ducing the Fe3O4 under-layer, cobalt ferrite nanocrystalline thin films with high coercivity can be obtained at lower post-annealing temperatures.展开更多
The conventional charge transport models based on density- and field-dependent mobility, only having a non-Arrhenius tem- perature dependence, cannot give good current-voltage characteristics of poly （2-methoxy-5-（2...The conventional charge transport models based on density- and field-dependent mobility, only having a non-Arrhenius tem- perature dependence, cannot give good current-voltage characteristics of poly （2-methoxy-5-（2＇-ethylhexyloxy）-p-phenylene vinylene） （MEH-PPV） hole-only devices. In this paper, we demonstrate that the current-voltage characteristics can give a good unified description of the temperature, carrier density mad electric field dependence of mobility based on both the Arrhenius temperature dependence and the non-Arrhenius temperature dependence. Fu^hermore, we perform a systematic study of charge transport and electrical properties for MEH-PPV. It is shown that the boundary carrier density has an important effect on the current-voltage characteristics. Too large or too small values of boundary carrier density will lead to incorrect cur- rent-voltage characteristics. The numerically calculated carrier density is a decreasing function of the distance to the interface, and the numerically calculated electric field is an increasing function of the distance. Both the maximum of carrier density and the minimum of electric field appear near the interface.展开更多
基金This project was financially supported by the Key Program of NSFC(No.90306015).
文摘The combination of ferromagnetic metal(FM)and semiconductor(SC)for spin injection was studied and demonstrated with FM-SC-FM junction.The semiconductor was chosen to be doped Indium-Tin-Oxide(ITO).Both ITO single-layer film and CoFe-ITO-CoFe junction were sputtering deposited.The ITO single-layer film was n-type with a small resistance of about 100Ω/Square.I-V curves and Magnetoresistance(MR)effect of the CoFe-ITO-CoFe junction were measured at room temperature and 77 K.Results show that the CoFe forms an ohmic contact to ITO film.But at low temperature,the I-V curves show a Schottky-like characteristic,which is strongly affect by applied magnetic field.The MR effect was measured to be 1%at 77 K,which indicates a spin injection into semiconductor to be realized in this sandwich junction.
基金support from the National Natural Science Foundation of China (Grant Nos. 10747007 and 11074179)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, the Ministry of Education
文摘The magnetic reversal mechanism has been determined within a micromagnetic model reliably for a two-phased magnetic nanosystem, with the formulae for nucleation fields derived analytically. It is found that the nucleation field HN decreases uni- formly as the size of the soft phase Ls increases whereas it increases with the size of the hard phase Lh. The analysis shows that whilst the effect of Lh could be ignored in most cases, where the nucleation field is dominated by the Ls and the calculation could be significantly simplified, the overly simple inverse square law between Hu and the soft layer thickness Ls adopted by the previous researchers is not a good approximation. While nucleation is the beginning of the magnetic reversal, pinning is the dominant coercivity mechanism in both two-phased and single-phased magnetic materials, where the crystalline defects exist. Comparison with the experimental data confirms this conclusion, indicating that Brown＇s paradox results from the much lower effective anisotropy in both single-phased and composite materials, as speculated in the literature.
基金supported by the National Natural Science Foundation of China (Grant No. 61071028)the NCET (Grant No. 08-0089)the RFDP (Grant No. 20100185110024)
文摘The microstructure and magnetic properties of cobalt ferrite thin films deposited by the sputtering method on an Fe3o4 un- der-layer were investigated at different post-annealing temperatures. Results show that the Fe3o4 under-layer can accelerate the grain growth of cobalt ferrite films due to the phase transformation of the Fe3o4 under-layer at about 400℃-500℃. By intro- ducing the Fe3O4 under-layer, cobalt ferrite nanocrystalline thin films with high coercivity can be obtained at lower post-annealing temperatures.
基金supported by the National Basic Research Program of China (Grant No.2007CB310407)Foundation for Innovative Research Groups of the NSFC (Grant No.61021061)+1 种基金the National Natural Science Foundation of China (Grant Nos.50972023 and 61071028)the International S&T Cooperation Program of China (Grant No.2006DFA53410)
文摘The conventional charge transport models based on density- and field-dependent mobility, only having a non-Arrhenius tem- perature dependence, cannot give good current-voltage characteristics of poly （2-methoxy-5-（2＇-ethylhexyloxy）-p-phenylene vinylene） （MEH-PPV） hole-only devices. In this paper, we demonstrate that the current-voltage characteristics can give a good unified description of the temperature, carrier density mad electric field dependence of mobility based on both the Arrhenius temperature dependence and the non-Arrhenius temperature dependence. Fu^hermore, we perform a systematic study of charge transport and electrical properties for MEH-PPV. It is shown that the boundary carrier density has an important effect on the current-voltage characteristics. Too large or too small values of boundary carrier density will lead to incorrect cur- rent-voltage characteristics. The numerically calculated carrier density is a decreasing function of the distance to the interface, and the numerically calculated electric field is an increasing function of the distance. Both the maximum of carrier density and the minimum of electric field appear near the interface.
