An oxide p-n heterojunction composed of a 150-nm La0.67Ca0.33 MnO3（LCMO） film, 0.05 wt% Nb doped SrTiO3 substrate（STON）, and sandwiched 5-nm LaAlO3（LAO） thin film is fabricated with the pulsed laser deposition t...An oxide p-n heterojunction composed of a 150-nm La0.67Ca0.33 MnO3（LCMO） film, 0.05 wt% Nb doped SrTiO3 substrate（STON）, and sandwiched 5-nm LaAlO3（LAO） thin film is fabricated with the pulsed laser deposition technique and the interfacial transport properties are experimentally studied. The rectifying behavior of the junction is in agreement with Newman＇s equation, indicating that tunneling is the dominant process for the carriers to pass through the interface while thermal emission is the dominant transport model of an LCMO/STON heterojunction with no LAO buffer layer.展开更多
An oxide p-n heterojunction composed of Pro.6Ca0.4MnO3 film, with a charge order （CO） transition, and lwt% Nb- doped SrTiO3 substrate is fabricated, and the transport properties of the interface are experimentally s...An oxide p-n heterojunction composed of Pro.6Ca0.4MnO3 film, with a charge order （CO） transition, and lwt% Nb- doped SrTiO3 substrate is fabricated, and the transport properties of the interface are experimentally studied. The rectifying behavior of the junction, well described by the Newman equation, is observed, indicating that tunneling is the dominant process by which the carriers pass through the interface. Above and below the CO transition temperature, satisfactory linear dependencies of junction resistance on temperature are observed, but the slopes of the two resistance-temperature relations are different. The CO process is believed to be relevant to this difference.展开更多
Interracial barrier is a key factor that determines the performances of heterojunctions. In this work, we study the effect of manganite film thickness on the effective interracial barrier for La0.67Sr0.33MnO3/Nb：SrTi...Interracial barrier is a key factor that determines the performances of heterojunctions. In this work, we study the effect of manganite film thickness on the effective interracial barrier for La0.67Sr0.33MnO3/Nb：SrTiO3 junctions, The barrier is extracted from the forward current-voltage characteristics. Our results demonstrate that the barrier decreases gradually from -0.85 eV to -0.60 eV when the film thickness decreases from 150 nm to 2 nm. The overall value of the barrier is only about 50% of the corresponding one determined from the photovoltaic effect.展开更多
A manganite p-n heterojunction composed of Lao.67Sro.33MnO3 film and 0.05 wt% Nb-doped SrTiO3 substrate is fabricated. Rectifying behavior of the junction well described by the Shockley equation is observed, and the t...A manganite p-n heterojunction composed of Lao.67Sro.33MnO3 film and 0.05 wt% Nb-doped SrTiO3 substrate is fabricated. Rectifying behavior of the junction well described by the Shockley equation is observed, and the transport properties of the interface are experimentally studied. A satisfactorily logarithmic linear dependence of resistance on temperature is observed in a temperature range of 150 K-380 K, and the linear relation between bias and activation energies deduced from the R - lIT curves is observed. According to activation energy, the interfacial barrier of the heterojunction is obtained, which is 0.91 eV.展开更多
Interface emission from heterojunction is a shortcoming for electroluminescent devices.A buffer layer introduced in the heterojunctional interfaces is a potential solution for the challenge.However,the dynamics for ca...Interface emission from heterojunction is a shortcoming for electroluminescent devices.A buffer layer introduced in the heterojunctional interfaces is a potential solution for the challenge.However,the dynamics for carrier tunneling to control the interface emission is still a mystery.Herein,the low-refractive HfO_(2)with a proper energy band configuration is em-ployed as the buffer layer in achieving ZnO-microwire/HfO_(2)/GaN heterojunctional light-emitting diodes(LEDs).The optic-ally pumped lasing threshold and lifetime of the ZnO microwire are reduced with the introduced HfO_(2)layer.As a result,the interface emission is of blue-shift from visible wavelengths to 394 nm whereas the ultraviolet(UV)emission is en-hanced.To regulate the interface recombination between electrons in the conduction band of ZnO and holes in the valence band of GaN,the tunneling electrons with higher conduction band are employed to produce a higher tunneling current through regulation of thin HfO_(2)film causing blue shift and interface emission enhancement.Our results provide a method to control the tunneling electrons in heterojunction for high-performance LEDs.展开更多
Based on the accurate and efficient thermal injection method, we develop a fully analytical surface potential model for the heterojunction tunnel field-effect transistor(H-TFET). This model accounts for both the effec...Based on the accurate and efficient thermal injection method, we develop a fully analytical surface potential model for the heterojunction tunnel field-effect transistor(H-TFET). This model accounts for both the effects of source depletion and inversion charge, which are the key factors influencing the charge, capacitance and current in H-TFET. The accuracy of the model is validated against TCAD simulation and is greatly improved in comparison with the conventional model based on Maxwell–Boltzmann approximation. Furthermore, the dependences of the surface potential and electric field on biases are well predicted and thoroughly analyzed.展开更多
We review colossal magnetoresistance in single phase manganites, as related to the field sensitive spin-charge interactions and phase separation; the rectifying property and negative/positive magnetoresistance in mang...We review colossal magnetoresistance in single phase manganites, as related to the field sensitive spin-charge interactions and phase separation; the rectifying property and negative/positive magnetoresistance in manganite/Nb：SrTio3 p-n junctions in relation to the special interface electronic structure; magnetoelectric coupling in manganite/ferroelectric structures that takes advantage of strain, carrier density, and magnetic field sensitivity; tunneling magnetoresistance in tunnel junctions with dielectric, ferroelectric, and organic semiconductor spacers using the fully spin polarized nature of manganites; and the effect of particle size on magnetic properties in manganite nanoparticles.展开更多
We reported a study of tunnel magnetoresistance(TMR)effect in single manganite nanowire via the combination of magnetotransport and magnetic force microscopy imaging.TMR value up to 290%has been observed in single(La1...We reported a study of tunnel magnetoresistance(TMR)effect in single manganite nanowire via the combination of magnetotransport and magnetic force microscopy imaging.TMR value up to 290%has been observed in single(La1-yPry)1-x CaxMnO3 nanowires with varying width.We find that the TMR effect can be explained in the scenario of opening and blockade of conducting channels from inherent magnetic domain evolutions.Our findings provide a new route to fabricate TMR junctions and point towards future improvements in complex oxide-based TMR spintronics.展开更多
A Ge/Si heterojunction L-shaped tunnel field-effect transistor combined with hetero-gate-dielectric （GHL-TFET） is proposed and investigated by TCAD simulation. Current-voltage characteristics, energy-band diagrams, ...A Ge/Si heterojunction L-shaped tunnel field-effect transistor combined with hetero-gate-dielectric （GHL-TFET） is proposed and investigated by TCAD simulation. Current-voltage characteristics, energy-band diagrams, and the distri- bution of the band-to-band tunneling （BTBT） generation rate of GHL-TFET are analyzed. In addition, the effect of the vertical channel width on the ON-current is studied and the thickness of the gate dielectric is optimized for better suppression of ambipolar current. Moreover, analog/RF figure-of-merits of GHL-TFET are also investigated in terms of the cut-off frequency and gain bandwidth production. Simulation results indicate that the ON-current of GHL-TFET is increased by about three orders of magnitude compared with that of the conventional L-shaped TFET. Besides, the introduction of the hetero-gate-dielectric not only suppresses the ambipolar current effectively but also improves the analog/RF performance drastically. It is demonstrated that the maximum cut-off frequency of GHL-TFET is about 160 GHz, which is 20 times higher than that of the conventional L-shaped TFET.展开更多
Here,an engineered tunneling layer enhanced photocurrent multiplication through the impact ionization effect was proposed and experimentally demonstrated on the graphene/silic on heterojunction photodetectors.With con...Here,an engineered tunneling layer enhanced photocurrent multiplication through the impact ionization effect was proposed and experimentally demonstrated on the graphene/silic on heterojunction photodetectors.With con sidering the suitable band structure of the insulation material and their special defect states,an atomic layer deposition(ALD)prepared wide-bandgap insulating(WBI)layer of AIN was introduced into the interface of graphene/silicon heterojunction.The promoted tunneling process from this designed structure dem on strated that can effectively help the impact ionization with photogain not only for the regular minority carriers from silicon,but also for the novel hot carries from graphene.As a result,significantly enhanced photocurrent as well as simultaneously decreased dark current about one order were accomplished in this graphene/insulation/silicon(GIS)heterojunction devices with the optimized AIN thickness of〜15 nm compared to the conventional graphene/silicon(GS)devices.Specifically,at the reverse bias of-10 V,a 3.96-A W_1 responsivity with the photogain of~5.8 for the peak response under 850-nm light illumination,and a 1.03-A W_1 responsivity with~3.5 photogain under the 365 nm ultraviolet(UV)illumination were realized,which are even remarkably higher than those in GIS devices with either AI2O3 or the commonly employed SiO2 insulation layers.This work dem on strates a universal strategy to fabricate broad ba nd,low-cost and high-performance photo-detecting devices towards the graphene-silicon optoelectronic integration.展开更多
Mixed-valence manganites have attracted considerable research focus in recent years not only because of the potential application of colossal magnetoresistance(CMR) in magnetic devices,but also because of many intrigu...Mixed-valence manganites have attracted considerable research focus in recent years not only because of the potential application of colossal magnetoresistance(CMR) in magnetic devices,but also because of many intriguing physical properties observed in these materials.Doping elements at A-site can alter the filling of 3d Mn band and the tolerance factor.Therefore the hole-and electron-doped CMR manganites exhibit a rich phase diagram.In addition,more theoretical and experimental results suggest that phase separation is a critical factor for the understanding of CMR phenomena.Recently,there is an increasing interest in the fabrication and investigation on manganite-based heterojunction,which demonstrated excellent rectifying property,large MR,and photovoltaic effect.展开更多
A novel photovoltaic phenomenon of internal photoemission was found in a low cost manganite La0.62Ca0.29K 0.09MnO3 (LCKMO)/zinc oxide (ZnO) heterojunction bilayers grown on ITO substrate by pulsed laser deposition (PL...A novel photovoltaic phenomenon of internal photoemission was found in a low cost manganite La0.62Ca0.29K 0.09MnO3 (LCKMO)/zinc oxide (ZnO) heterojunction bilayers grown on ITO substrate by pulsed laser deposition (PLD) at relative low growth temperature. The heterostructure ITO/LCKMO/ZnO/Al exhibits reproducible rectifying characteristics and light current under continuous laser irradiation of = 325 nm. We report here the influence of LCKMO/ZnO bilayers' thickness on the electrical and photoelectric properties of the heterostructure at room temperature. The power conversion efficiency (PCE) is achieved when the LCKMO and ZnO layers are thin enough or the full space charge layer is sufficient. We obtained the maximum value of PCE of 0.0145% when the thicknesses of LCKMO and ZnO layers are 25 and 150 nm, respectively. The open circuit voltage is 0.04 V under this condition due to the internal photoemission.展开更多
Samples with nominal composition of （1 - x）La0.67Ca0.33MnO3 （LCMO）/xCuO （x = 0%, 2%, 4% and 20% ） were made using a special experimental method. The temperature dependence of the resistivity （ρ） of the compos...Samples with nominal composition of （1 - x）La0.67Ca0.33MnO3 （LCMO）/xCuO （x = 0%, 2%, 4% and 20% ） were made using a special experimental method. The temperature dependence of the resistivity （ρ） of the composites was investigated in the temperature range of 10 - 300 K and different magnetic fields of H = 0, 0.1, 0.3, 0.5, 1.0 and 3.0 T. The results showed that CuO percentage x had important effects on metal-insulator transition temperature （Tp）, zero field peak resistivity （ρmax）, and magnetoresistance （MR） properties of the composites. Tp shifted sharply towards low temperature with the increase of x in the range of x ≤4%, but was almost independent of x at high level of CuO content. Composites with x = 4 % and 20 % exhibited similar electrical transmission behavior. Compared with pure LCMO, enhanced magnetoresistance could be clearly observed even in a quite low magnetic field of 0.3 T. For x =4% and 20% samples, the MR value at 0.3 T could reach as high as - 88% and - 90%, respectively. XRD and SEM analysis showed that the substantial enhancement of MR, especially near Tp, was because of local spin disorder between contiguous LCMO ferromagnetic particles caused by the addition of CuO.展开更多
The composites La0.6Sm0. 1Sr0.3MnO3 ＋ x CoO （x = 0.0, 0.1, 0.2, 0.3, 0.4 mol）, named as A x samples, were synthesized by the sol-gel technique to derive homogeneous CoO-coated composites. CoO addition induces an in...The composites La0.6Sm0. 1Sr0.3MnO3 ＋ x CoO （x = 0.0, 0.1, 0.2, 0.3, 0.4 mol）, named as A x samples, were synthesized by the sol-gel technique to derive homogeneous CoO-coated composites. CoO addition induces an increase of resistivity （ρ） and a decrease of Curie temperature （TC）, magnetization, and Tpat which the p peak is located. It has been concluded that the resistivity below Tp fits well with the equation ρ = ρ0 ＋ ρ2 T^2 ＋ ρ4.5 T^4.5, indicating the importance of grain/domain boundary effects, the electron-electron scattering process, and the two magnon scattering process. On the other hand, the paramagnetic insulating region may be explained by using adiabatic small polaron hopping mechanism, thereby indicating that polaron hopping might be responsible for the conduction mechanism. Magnetoresistance results were explained by a two-level model of tunneling MR and percolation model.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.10804089)
文摘An oxide p-n heterojunction composed of a 150-nm La0.67Ca0.33 MnO3（LCMO） film, 0.05 wt% Nb doped SrTiO3 substrate（STON）, and sandwiched 5-nm LaAlO3（LAO） thin film is fabricated with the pulsed laser deposition technique and the interfacial transport properties are experimentally studied. The rectifying behavior of the junction is in agreement with Newman＇s equation, indicating that tunneling is the dominant process for the carriers to pass through the interface while thermal emission is the dominant transport model of an LCMO/STON heterojunction with no LAO buffer layer.
基金Project supported by the National Natural Science Foundation of China(Grant No.10804089)
文摘An oxide p-n heterojunction composed of Pro.6Ca0.4MnO3 film, with a charge order （CO） transition, and lwt% Nb- doped SrTiO3 substrate is fabricated, and the transport properties of the interface are experimentally studied. The rectifying behavior of the junction, well described by the Newman equation, is observed, indicating that tunneling is the dominant process by which the carriers pass through the interface. Above and below the CO transition temperature, satisfactory linear dependencies of junction resistance on temperature are observed, but the slopes of the two resistance-temperature relations are different. The CO process is believed to be relevant to this difference.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10804094,50832007,50721001 and 50821001)the Natural Science Foundation of Hebei Province,China (Grant No. A2009000339)
文摘Interracial barrier is a key factor that determines the performances of heterojunctions. In this work, we study the effect of manganite film thickness on the effective interracial barrier for La0.67Sr0.33MnO3/Nb：SrTiO3 junctions, The barrier is extracted from the forward current-voltage characteristics. Our results demonstrate that the barrier decreases gradually from -0.85 eV to -0.60 eV when the film thickness decreases from 150 nm to 2 nm. The overall value of the barrier is only about 50% of the corresponding one determined from the photovoltaic effect.
基金Project supported by the National Natural Science Foundation of China(Grant No.10804089)
文摘A manganite p-n heterojunction composed of Lao.67Sro.33MnO3 film and 0.05 wt% Nb-doped SrTiO3 substrate is fabricated. Rectifying behavior of the junction well described by the Shockley equation is observed, and the transport properties of the interface are experimentally studied. A satisfactorily logarithmic linear dependence of resistance on temperature is observed in a temperature range of 150 K-380 K, and the linear relation between bias and activation energies deduced from the R - lIT curves is observed. According to activation energy, the interfacial barrier of the heterojunction is obtained, which is 0.91 eV.
基金Ths work was supported by NSFC(11734005.62075041,61821002)Na tional Key Research and Development Program of China(2018YFA0209101,2017YFA0700500).
文摘Interface emission from heterojunction is a shortcoming for electroluminescent devices.A buffer layer introduced in the heterojunctional interfaces is a potential solution for the challenge.However,the dynamics for carrier tunneling to control the interface emission is still a mystery.Herein,the low-refractive HfO_(2)with a proper energy band configuration is em-ployed as the buffer layer in achieving ZnO-microwire/HfO_(2)/GaN heterojunctional light-emitting diodes(LEDs).The optic-ally pumped lasing threshold and lifetime of the ZnO microwire are reduced with the introduced HfO_(2)layer.As a result,the interface emission is of blue-shift from visible wavelengths to 394 nm whereas the ultraviolet(UV)emission is en-hanced.To regulate the interface recombination between electrons in the conduction band of ZnO and holes in the valence band of GaN,the tunneling electrons with higher conduction band are employed to produce a higher tunneling current through regulation of thin HfO_(2)film causing blue shift and interface emission enhancement.Our results provide a method to control the tunneling electrons in heterojunction for high-performance LEDs.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10574036 and 10574U37, and Natural Science Foundation of Hebei Province of China under Grant Nos. A2004000141 and 2005000143
基金Project supported in part by the National Natural Science Foundation of China (Grant No. 62104192)in part by the Natural Science Basic Research Program of Shaanxi Province (Grant No. 2021JQ-717)。
文摘Based on the accurate and efficient thermal injection method, we develop a fully analytical surface potential model for the heterojunction tunnel field-effect transistor(H-TFET). This model accounts for both the effects of source depletion and inversion charge, which are the key factors influencing the charge, capacitance and current in H-TFET. The accuracy of the model is validated against TCAD simulation and is greatly improved in comparison with the conventional model based on Maxwell–Boltzmann approximation. Furthermore, the dependences of the surface potential and electric field on biases are well predicted and thoroughly analyzed.
基金supported by the National Natural Science Foundation of Chinathe National Basic Research Program of China(Grant Nos.2012CB922003,2011CBA00102,and 2009CB929502)
文摘We review colossal magnetoresistance in single phase manganites, as related to the field sensitive spin-charge interactions and phase separation; the rectifying property and negative/positive magnetoresistance in manganite/Nb：SrTio3 p-n junctions in relation to the special interface electronic structure; magnetoelectric coupling in manganite/ferroelectric structures that takes advantage of strain, carrier density, and magnetic field sensitivity; tunneling magnetoresistance in tunnel junctions with dielectric, ferroelectric, and organic semiconductor spacers using the fully spin polarized nature of manganites; and the effect of particle size on magnetic properties in manganite nanoparticles.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0300702)Shanghai Municipal Natural Science Foundation,China(Grant Nos.19ZR1402800,18JC1411400,18ZR1403200,and 17ZR1442600)+1 种基金the Program of Shanghai Academic Research Leader,China(Grant Nos.18XD1400600 and 17XD1400400)the China Postdoctoral Science Foundation(Grant Nos.2016M601488 and 2017T100265)
文摘We reported a study of tunnel magnetoresistance(TMR)effect in single manganite nanowire via the combination of magnetotransport and magnetic force microscopy imaging.TMR value up to 290%has been observed in single(La1-yPry)1-x CaxMnO3 nanowires with varying width.We find that the TMR effect can be explained in the scenario of opening and blockade of conducting channels from inherent magnetic domain evolutions.Our findings provide a new route to fabricate TMR junctions and point towards future improvements in complex oxide-based TMR spintronics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61574109 and 61204092)
文摘A Ge/Si heterojunction L-shaped tunnel field-effect transistor combined with hetero-gate-dielectric （GHL-TFET） is proposed and investigated by TCAD simulation. Current-voltage characteristics, energy-band diagrams, and the distri- bution of the band-to-band tunneling （BTBT） generation rate of GHL-TFET are analyzed. In addition, the effect of the vertical channel width on the ON-current is studied and the thickness of the gate dielectric is optimized for better suppression of ambipolar current. Moreover, analog/RF figure-of-merits of GHL-TFET are also investigated in terms of the cut-off frequency and gain bandwidth production. Simulation results indicate that the ON-current of GHL-TFET is increased by about three orders of magnitude compared with that of the conventional L-shaped TFET. Besides, the introduction of the hetero-gate-dielectric not only suppresses the ambipolar current effectively but also improves the analog/RF performance drastically. It is demonstrated that the maximum cut-off frequency of GHL-TFET is about 160 GHz, which is 20 times higher than that of the conventional L-shaped TFET.
基金the National Basic Research Program of China(Grant No.2017YFB0404101 and 2018YFB0406700)National Natural Science Foundation of China(Grant No.61505172 and 61675173)+2 种基金Natural Science Foundation of Fujian Province of China(Grant No.2018J01102)Natural Science Foundation of Jiangxi Province of China(20202ACB214008)the Open Fund of the State Key Laboratory of In teg rated Optoelectronics(IOSKL2020KF12).
文摘Here,an engineered tunneling layer enhanced photocurrent multiplication through the impact ionization effect was proposed and experimentally demonstrated on the graphene/silic on heterojunction photodetectors.With con sidering the suitable band structure of the insulation material and their special defect states,an atomic layer deposition(ALD)prepared wide-bandgap insulating(WBI)layer of AIN was introduced into the interface of graphene/silicon heterojunction.The promoted tunneling process from this designed structure dem on strated that can effectively help the impact ionization with photogain not only for the regular minority carriers from silicon,but also for the novel hot carries from graphene.As a result,significantly enhanced photocurrent as well as simultaneously decreased dark current about one order were accomplished in this graphene/insulation/silicon(GIS)heterojunction devices with the optimized AIN thickness of〜15 nm compared to the conventional graphene/silicon(GS)devices.Specifically,at the reverse bias of-10 V,a 3.96-A W_1 responsivity with the photogain of~5.8 for the peak response under 850-nm light illumination,and a 1.03-A W_1 responsivity with~3.5 photogain under the 365 nm ultraviolet(UV)illumination were realized,which are even remarkably higher than those in GIS devices with either AI2O3 or the commonly employed SiO2 insulation layers.This work dem on strates a universal strategy to fabricate broad ba nd,low-cost and high-performance photo-detecting devices towards the graphene-silicon optoelectronic integration.
基金supported by the National Natural Science Foundation of China(Grant Nos.10774146,10974205,10904150 and 11274313)Anhui Provincial Natural Science Foundation(Grant No.1208085MA06)+1 种基金Joint Funds of the National Natural Science Foundation of China and the Chinese Academy of Sciences' Large-scale Scientific Facility(Grant No. U1232138)support by the National Key Basic Research(Grant No. 2011CBA00111)
文摘Mixed-valence manganites have attracted considerable research focus in recent years not only because of the potential application of colossal magnetoresistance(CMR) in magnetic devices,but also because of many intriguing physical properties observed in these materials.Doping elements at A-site can alter the filling of 3d Mn band and the tolerance factor.Therefore the hole-and electron-doped CMR manganites exhibit a rich phase diagram.In addition,more theoretical and experimental results suggest that phase separation is a critical factor for the understanding of CMR phenomena.Recently,there is an increasing interest in the fabrication and investigation on manganite-based heterojunction,which demonstrated excellent rectifying property,large MR,and photovoltaic effect.
基金supported by the National Natural Science Foundation of China (No. 90922034 and No. 21131002)Specialized Research Fund for the Doctoral Program of Higher Education (No. 20110061130005)
文摘A novel photovoltaic phenomenon of internal photoemission was found in a low cost manganite La0.62Ca0.29K 0.09MnO3 (LCKMO)/zinc oxide (ZnO) heterojunction bilayers grown on ITO substrate by pulsed laser deposition (PLD) at relative low growth temperature. The heterostructure ITO/LCKMO/ZnO/Al exhibits reproducible rectifying characteristics and light current under continuous laser irradiation of = 325 nm. We report here the influence of LCKMO/ZnO bilayers' thickness on the electrical and photoelectric properties of the heterostructure at room temperature. The power conversion efficiency (PCE) is achieved when the LCKMO and ZnO layers are thin enough or the full space charge layer is sufficient. We obtained the maximum value of PCE of 0.0145% when the thicknesses of LCKMO and ZnO layers are 25 and 150 nm, respectively. The open circuit voltage is 0.04 V under this condition due to the internal photoemission.
基金Project supported by the National Natural Science Foundation of China (10374032)
文摘Samples with nominal composition of （1 - x）La0.67Ca0.33MnO3 （LCMO）/xCuO （x = 0%, 2%, 4% and 20% ） were made using a special experimental method. The temperature dependence of the resistivity （ρ） of the composites was investigated in the temperature range of 10 - 300 K and different magnetic fields of H = 0, 0.1, 0.3, 0.5, 1.0 and 3.0 T. The results showed that CuO percentage x had important effects on metal-insulator transition temperature （Tp）, zero field peak resistivity （ρmax）, and magnetoresistance （MR） properties of the composites. Tp shifted sharply towards low temperature with the increase of x in the range of x ≤4%, but was almost independent of x at high level of CuO content. Composites with x = 4 % and 20 % exhibited similar electrical transmission behavior. Compared with pure LCMO, enhanced magnetoresistance could be clearly observed even in a quite low magnetic field of 0.3 T. For x =4% and 20% samples, the MR value at 0.3 T could reach as high as - 88% and - 90%, respectively. XRD and SEM analysis showed that the substantial enhancement of MR, especially near Tp, was because of local spin disorder between contiguous LCMO ferromagnetic particles caused by the addition of CuO.
基金Project supported by NSFof Fujian Province (E0320002 ,2005K020) and Fumiao Foundation of Fujian Normal University (12F032)
文摘The composites La0.6Sm0. 1Sr0.3MnO3 ＋ x CoO （x = 0.0, 0.1, 0.2, 0.3, 0.4 mol）, named as A x samples, were synthesized by the sol-gel technique to derive homogeneous CoO-coated composites. CoO addition induces an increase of resistivity （ρ） and a decrease of Curie temperature （TC）, magnetization, and Tpat which the p peak is located. It has been concluded that the resistivity below Tp fits well with the equation ρ = ρ0 ＋ ρ2 T^2 ＋ ρ4.5 T^4.5, indicating the importance of grain/domain boundary effects, the electron-electron scattering process, and the two magnon scattering process. On the other hand, the paramagnetic insulating region may be explained by using adiabatic small polaron hopping mechanism, thereby indicating that polaron hopping might be responsible for the conduction mechanism. Magnetoresistance results were explained by a two-level model of tunneling MR and percolation model.
