Co−TiO2 nanocomposite films were prepared via magnetron sputtering at various substrate temperatures.The films comprise Co particles dispersed in an amorphous TiO2 matrix and exhibit coexisting ferromagnetic and super...Co−TiO2 nanocomposite films were prepared via magnetron sputtering at various substrate temperatures.The films comprise Co particles dispersed in an amorphous TiO2 matrix and exhibit coexisting ferromagnetic and superparamagnetic properties.When the substrate temperature increases from room temperature to 400℃,Co particles gradually grow,and the degree of Co oxidation significantly decreases.Consequently,the saturation magnetization increases from 0.13 to 0.43 T at the same Co content by increasing the substrate temperature from room temperature to 400℃.At a high substrate temperature,conductive pathways form among some of the clustered Co particles.Thus,resistivity rapidly declines from 1600 to 76μΩ·m.The magnetoresistive characteristic of Co−TiO2 films is achieved even at resistivity of as low as 76μΩ·m.These results reveal that the obtained nanocomposite films have low Co oxidation,high magnetization and magnetoresistance at room temperature.展开更多
The tunneling conductance and tunneling magnetoresistance(TMR)are investigated in ferromagnet/insulator/ferromagnet/insulator/d-wave superconductor(FM/I/FM/I/d-wave SC)structures by applying an extended Blonder-Tinkha...The tunneling conductance and tunneling magnetoresistance(TMR)are investigated in ferromagnet/insulator/ferromagnet/insulator/d-wave superconductor(FM/I/FM/I/d-wave SC)structures by applying an extended Blonder-Tinkham-Klapwijk(BTK)approach.We study the effects of the exchange splitting in the FM, the magnetic impurity scattering in the thin insulator interface of FM/I/FM,and noncollinear magnetizations in adja- cent magnetic layers on the TMR.It is shown(1)that the tunneling conductance and TMR exhibit amplitude-varying oscillating behavior with exchange splitting,(2)that with the presence of spin-flip scattering in insulator interface of FM/I/FM,the TMR can be dramatically enhanced,and(3)that the TMR depends strongly on the angle between the magnetization of two FMs.展开更多
The longitudinal ultrasonic velocity （V1）, attenuation （α1）, magnetization and resistivity of single phase polycrystalline La1/3Sr2/3CoO3 were measured as a function of temperature from 20 K to 300 K. The resisti...The longitudinal ultrasonic velocity （V1）, attenuation （α1）, magnetization and resistivity of single phase polycrystalline La1/3Sr2/3CoO3 were measured as a function of temperature from 20 K to 300 K. The resistivity shows metallic behavior in the whole temperature range and a kink at 235 K was observed, which coincides with the ferromagnetic transition temperature （Tc）. As the temperature cools down from Tc, the V1 softens conspicuously at beginning and reaches a minimum at 120 K. After that the V1 dramatically stiffens below 120 K accompanied by a wide attenuation peak. The analysis of the results suggests that these ultrasonic anomalies ;nay correspond to local lattice distortions via the Jahn-Teller effect of intermediate spin Co^3＋.展开更多
基金Project(2016YFE0205700)supported by the National Key Research and Development Program of ChinaProject(18JCYBJC18000)supported by the Natural Science Foundation of Tianjin City,China。
文摘Co−TiO2 nanocomposite films were prepared via magnetron sputtering at various substrate temperatures.The films comprise Co particles dispersed in an amorphous TiO2 matrix and exhibit coexisting ferromagnetic and superparamagnetic properties.When the substrate temperature increases from room temperature to 400℃,Co particles gradually grow,and the degree of Co oxidation significantly decreases.Consequently,the saturation magnetization increases from 0.13 to 0.43 T at the same Co content by increasing the substrate temperature from room temperature to 400℃.At a high substrate temperature,conductive pathways form among some of the clustered Co particles.Thus,resistivity rapidly declines from 1600 to 76μΩ·m.The magnetoresistive characteristic of Co−TiO2 films is achieved even at resistivity of as low as 76μΩ·m.These results reveal that the obtained nanocomposite films have low Co oxidation,high magnetization and magnetoresistance at room temperature.
基金The project supported by Natural Science Foundation of the Education Bureau of Jiangsu Province of China under Grant No.01KJB140007the“333”Program of Jiangsu Province of China
文摘The tunneling conductance and tunneling magnetoresistance(TMR)are investigated in ferromagnet/insulator/ferromagnet/insulator/d-wave superconductor(FM/I/FM/I/d-wave SC)structures by applying an extended Blonder-Tinkham-Klapwijk(BTK)approach.We study the effects of the exchange splitting in the FM, the magnetic impurity scattering in the thin insulator interface of FM/I/FM,and noncollinear magnetizations in adja- cent magnetic layers on the TMR.It is shown(1)that the tunneling conductance and TMR exhibit amplitude-varying oscillating behavior with exchange splitting,(2)that with the presence of spin-flip scattering in insulator interface of FM/I/FM,the TMR can be dramatically enhanced,and(3)that the TMR depends strongly on the angle between the magnetization of two FMs.
基金This work was supported by the National Natural Science Foundation of China （No.10774136）.
文摘The longitudinal ultrasonic velocity （V1）, attenuation （α1）, magnetization and resistivity of single phase polycrystalline La1/3Sr2/3CoO3 were measured as a function of temperature from 20 K to 300 K. The resistivity shows metallic behavior in the whole temperature range and a kink at 235 K was observed, which coincides with the ferromagnetic transition temperature （Tc）. As the temperature cools down from Tc, the V1 softens conspicuously at beginning and reaches a minimum at 120 K. After that the V1 dramatically stiffens below 120 K accompanied by a wide attenuation peak. The analysis of the results suggests that these ultrasonic anomalies ;nay correspond to local lattice distortions via the Jahn-Teller effect of intermediate spin Co^3＋.
