Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd a...Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd and Ag addition induce a decrease in resistivity and an increase in temperature at which the resistivity reaches its maximum. This is mainly due to the improvement of grain boundaries caused by the segregation of good conductive metal grains on the grain boundaries/surfaces. In addition, both Pd and Ag addition induce a large enhancement of room temperature magnetoresistance （RTMR）. Note that 27% molar ratio of Ag addition induces a large RTMR of about 70%, about ten times larger than pure LCBMO, whereas 27% molar ratio Pd addition brings a much larger RTMR of about 170%. The large enhancements of MR can be attributed to the decrease in resistivity of the samples caused by the good conductive metal. On the other hand, the polarization of Pd atoms near the Mn ions on the grain surfaces/boundaries plays a very im-portant role in the increase in MR, which induces a large number of spin clusters in Pd-added samples.展开更多
Rb-substitued Pr1-xRbxMnO3（0.05≤x≤0.08） reaction. Powder X-ray diffraction showed that the space group of Pnma. Spin glass behaviors was successfully synthesized by solid state all the compounds were orthorhombic...Rb-substitued Pr1-xRbxMnO3（0.05≤x≤0.08） reaction. Powder X-ray diffraction showed that the space group of Pnma. Spin glass behaviors was successfully synthesized by solid state all the compounds were orthorhombic with were observed for all the compounds at low temperature, suggesting the competition between ferromagnetic and antiferromagnetic. The temperature dependence of the resistivity for the compound Pr0.92Rb0.0sMnO3.02 at 0 and 2 T magnetic field was also investigated. The compound shows semiconducting behavior, and the band gap is 0.3 eV. The maximum magnetoresistance is about 30% at 2 T magnetic field near 116 K.展开更多
Within the t-J model, the charge transport and spin response of the doped bilayer triangular antiferromagnetare studied by considering the bilayer interaction. Although the bilayer interaction leads to the band splitt...Within the t-J model, the charge transport and spin response of the doped bilayer triangular antiferromagnetare studied by considering the bilayer interaction. Although the bilayer interaction leads to the band splitting in theelectronic structure, the qualitative behaviors of the physical properties are the same as in the single layer case. Theconductivity spectrum shows the low-energy peak and unusual midinfrared band, the temperature-dependent resistivityis characterized by the nonlinearity metallic-like behavior in the higher temperature range and the deviation from themetallic-like behavior in the lower temperature range and the commensurate neutron scattering peak near the half-fillingis split into six incommensurate peaks in the underdoped regime, with the incommensurability increasing with the holeconcentration at lower dopings, and saturating at higher dopings.展开更多
We investigate the linear and nonlinear transport through a single level quantum dot connected to two ferromagnetic leads in Kondo regime, using the slave-boson mean-field approach for finite on-site Coulomb repulsion...We investigate the linear and nonlinear transport through a single level quantum dot connected to two ferromagnetic leads in Kondo regime, using the slave-boson mean-field approach for finite on-site Coulomb repulsion. We find that for antiparallel alignment of the spin orientations in the leads, a single zero-bias Kondo peak always appears in the voltage-dependent differential conductance with peak height going down to zero as the polarization grows to P = 1.For parallel configuration, with increasing polarization from zero, the Kondo peak descends and greatly widens with the appearance of shoulders, and finally splits into two peaks on both sides of the bias voltage around P ～ 0.7 until disappearing at even larger polarization strength. At any spin orientation angle θ, the linear conductance generally drops with growing polarization strength. For a given finite polarization, the minimum linear conductance always appears at θ = π.展开更多
We study the magnetic field effects on the spin-polarized transport of the quantum dot （QD） spin valve in the sequential tunneling regime. A set of generalized master equation is derived. Based on that, we discuss t...We study the magnetic field effects on the spin-polarized transport of the quantum dot （QD） spin valve in the sequential tunneling regime. A set of generalized master equation is derived. Based on that, we discuss the collinear and noncollinear magnetic field effects, respectively. In the collinear magnetic field case, we find that the Zeeman splitting can induce a negative differential conductance （NDC）, which is quite different from the one found in previous studies. It has a critical polarization in the parallel arrangement and will disappear in the antiparallel configuration. In the noncollinear magnetic field case, the current shows two plateaus and their angular dependence is analyzed. Although sometimes the two current plateaus have similar angular dependence, their mechanisms are different. Our formalism is also suitable for calculating the transport in magnetic molecules, in which the spin splitting is induced not by a magnetic field but by the intrinsic magnetization.展开更多
We present a comprehensive view and details of calculations on Aharonov-Anandan phase for the charged particles in the external electric and magnetic fields for a nonadiabatic process.We derive,with consideration of a...We present a comprehensive view and details of calculations on Aharonov-Anandan phase for the charged particles in the external electric and magnetic fields for a nonadiabatic process.We derive,with consideration of a spin-orbit interaction and Zeemann Splitting,the persistent currents as a response to an Aharonov-Casher topological interference effect in one-dimensional mesoscopic ring.We also establish a connection to Berry adiabatic phase with deduced dynamical-nature dependence in the nonadiabatic process.The second quantization representation has also been employed in exhibition of persistent currents in the many-body case.展开更多
Charge carriers in organic semiconductor are different from that of traditional inorganic semiconductor. Based on three-current model, considering electrical field effect, we present a theoretical model to discuss spi...Charge carriers in organic semiconductor are different from that of traditional inorganic semiconductor. Based on three-current model, considering electrical field effect, we present a theoretical model to discuss spin-polarized injection from ferromagnetic electrode into organic semiconductor by analyzing electrochemical potential both in ferromagnetic electrode and organic semiconductors. The calculated result of this model shows effects of electrode＇s spin polarization, equilibrium value of polarons ratio, interracial conductance, bulk conductivity of materials and electrical field. It is found that we could get decent spin polarization with common ferromagnetic electrode by increasing equilibrium value of polarons ratio. We also find that large and matched bulk conductivity of organic semiconductor and electrode, small spin-dependent interracial conductance, and enough large electrical field are critical factors for increasing spin polarization.展开更多
Manipulation of spin states via purely electric means forms the research branch "all-electric spintronics".In this paper,we briefly review recent progress relating to the all-electric spintronics,including e...Manipulation of spin states via purely electric means forms the research branch "all-electric spintronics".In this paper,we briefly review recent progress relating to the all-electric spintronics,including electric-field control of Rashba spin-orbit coupling,magnetic anisotropy,exchange bias,ferromagnetism,and other forms of magnetoelectric coupling.Special focus is given to surface/interface systems,including semiconductor(oxide) heterostructures,magnetic/nonmagnetic surfaces,semiconductor-metal interfaces,and other nanostructures,which can be good candidates for functional materials for spintronic.展开更多
With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead...With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead to the idea of spintronics.A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical models.In addition,the mechanisms of various magnetoresistance beyond the GMR are reviewed,for instance,tunnelling magnetoresistance,colossal magnetoresistance,and magnetoresistance in ferromagnetic semiconductors,nanowires,organic spintronics and non-magnetic systems.展开更多
文摘Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd and Ag addition induce a decrease in resistivity and an increase in temperature at which the resistivity reaches its maximum. This is mainly due to the improvement of grain boundaries caused by the segregation of good conductive metal grains on the grain boundaries/surfaces. In addition, both Pd and Ag addition induce a large enhancement of room temperature magnetoresistance （RTMR）. Note that 27% molar ratio of Ag addition induces a large RTMR of about 70%, about ten times larger than pure LCBMO, whereas 27% molar ratio Pd addition brings a much larger RTMR of about 170%. The large enhancements of MR can be attributed to the decrease in resistivity of the samples caused by the good conductive metal. On the other hand, the polarization of Pd atoms near the Mn ions on the grain surfaces/boundaries plays a very im-portant role in the increase in MR, which induces a large number of spin clusters in Pd-added samples.
文摘Rb-substitued Pr1-xRbxMnO3（0.05≤x≤0.08） reaction. Powder X-ray diffraction showed that the space group of Pnma. Spin glass behaviors was successfully synthesized by solid state all the compounds were orthorhombic with were observed for all the compounds at low temperature, suggesting the competition between ferromagnetic and antiferromagnetic. The temperature dependence of the resistivity for the compound Pr0.92Rb0.0sMnO3.02 at 0 and 2 T magnetic field was also investigated. The compound shows semiconducting behavior, and the band gap is 0.3 eV. The maximum magnetoresistance is about 30% at 2 T magnetic field near 116 K.
文摘Within the t-J model, the charge transport and spin response of the doped bilayer triangular antiferromagnetare studied by considering the bilayer interaction. Although the bilayer interaction leads to the band splitting in theelectronic structure, the qualitative behaviors of the physical properties are the same as in the single layer case. Theconductivity spectrum shows the low-energy peak and unusual midinfrared band, the temperature-dependent resistivityis characterized by the nonlinearity metallic-like behavior in the higher temperature range and the deviation from themetallic-like behavior in the lower temperature range and the commensurate neutron scattering peak near the half-fillingis split into six incommensurate peaks in the underdoped regime, with the incommensurability increasing with the holeconcentration at lower dopings, and saturating at higher dopings.
文摘We investigate the linear and nonlinear transport through a single level quantum dot connected to two ferromagnetic leads in Kondo regime, using the slave-boson mean-field approach for finite on-site Coulomb repulsion. We find that for antiparallel alignment of the spin orientations in the leads, a single zero-bias Kondo peak always appears in the voltage-dependent differential conductance with peak height going down to zero as the polarization grows to P = 1.For parallel configuration, with increasing polarization from zero, the Kondo peak descends and greatly widens with the appearance of shoulders, and finally splits into two peaks on both sides of the bias voltage around P ～ 0.7 until disappearing at even larger polarization strength. At any spin orientation angle θ, the linear conductance generally drops with growing polarization strength. For a given finite polarization, the minimum linear conductance always appears at θ = π.
基金supported by the Chinese Academy of Sciences,US-DOE under Grant No.DE-FG02-04ER46124,US-Natural Science FoundationNational Natural Science Foundation of China under Grant Nos.10525418,10734110,and 60776060
文摘We study the magnetic field effects on the spin-polarized transport of the quantum dot （QD） spin valve in the sequential tunneling regime. A set of generalized master equation is derived. Based on that, we discuss the collinear and noncollinear magnetic field effects, respectively. In the collinear magnetic field case, we find that the Zeeman splitting can induce a negative differential conductance （NDC）, which is quite different from the one found in previous studies. It has a critical polarization in the parallel arrangement and will disappear in the antiparallel configuration. In the noncollinear magnetic field case, the current shows two plateaus and their angular dependence is analyzed. Although sometimes the two current plateaus have similar angular dependence, their mechanisms are different. Our formalism is also suitable for calculating the transport in magnetic molecules, in which the spin splitting is induced not by a magnetic field but by the intrinsic magnetization.
基金The project supported by National Natural Science Foundation of China under Grant Nos.90103077 and 10274069Natural Science Foundation of Guangdong Province of China under Grant No.011151
文摘We present a comprehensive view and details of calculations on Aharonov-Anandan phase for the charged particles in the external electric and magnetic fields for a nonadiabatic process.We derive,with consideration of a spin-orbit interaction and Zeemann Splitting,the persistent currents as a response to an Aharonov-Casher topological interference effect in one-dimensional mesoscopic ring.We also establish a connection to Berry adiabatic phase with deduced dynamical-nature dependence in the nonadiabatic process.The second quantization representation has also been employed in exhibition of persistent currents in the many-body case.
基金Supported by the Natural Science Foundation of Shandong Province under Grant No.Y2006A18 the Key Programme of Nature Foundation of Shandong Jianzhu University under Grant No.XZ050102
文摘Charge carriers in organic semiconductor are different from that of traditional inorganic semiconductor. Based on three-current model, considering electrical field effect, we present a theoretical model to discuss spin-polarized injection from ferromagnetic electrode into organic semiconductor by analyzing electrochemical potential both in ferromagnetic electrode and organic semiconductors. The calculated result of this model shows effects of electrode＇s spin polarization, equilibrium value of polarons ratio, interracial conductance, bulk conductivity of materials and electrical field. It is found that we could get decent spin polarization with common ferromagnetic electrode by increasing equilibrium value of polarons ratio. We also find that large and matched bulk conductivity of organic semiconductor and electrode, small spin-dependent interracial conductance, and enough large electrical field are critical factors for increasing spin polarization.
基金supported by the National Basic Research Program of China(Grant No.2013CB922300)the National Natural Science Foundation of China(Grant Nos.11004211,61125403 and 50832003)+1 种基金PCSIRT, NCET,ECNU Fostering Project for Top Doctoral DissertationsFundamental Research Funds for the central universities(ECNU)
文摘Manipulation of spin states via purely electric means forms the research branch "all-electric spintronics".In this paper,we briefly review recent progress relating to the all-electric spintronics,including electric-field control of Rashba spin-orbit coupling,magnetic anisotropy,exchange bias,ferromagnetism,and other forms of magnetoelectric coupling.Special focus is given to surface/interface systems,including semiconductor(oxide) heterostructures,magnetic/nonmagnetic surfaces,semiconductor-metal interfaces,and other nanostructures,which can be good candidates for functional materials for spintronic.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51125004,10974120,B13029 and JQ200901)the National Basic Research Program of China (Grant Nos. 2013CB922303and 2009CB929202)
文摘With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead to the idea of spintronics.A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical models.In addition,the mechanisms of various magnetoresistance beyond the GMR are reviewed,for instance,tunnelling magnetoresistance,colossal magnetoresistance,and magnetoresistance in ferromagnetic semiconductors,nanowires,organic spintronics and non-magnetic systems.
