共查询到20条相似文献,搜索用时 15 毫秒
1.
Current–voltage (J–V) characteristics of epitaxial hetero-junctions composed of Pr0.7Ca0.3MnO3 and Nb:SrTiO3 were studied under forward and reversed bias conditions. Detailed analysis showed that the J–V characteristics of these heterojunctions can be well-fitted by the thermally-assisted tunnelling model. While the dielectric constant of Nb:SrTiO3 extracted under the forward bias was about one order of magnitude smaller than that of bulk SrTiO3, the value obtained under reverse bias was very close to that of the bulk SrTiO3. The result can be explained by the existence of an interface layer on the Nb:SrTiO3 substrate with a smaller effective dielectric constant. The current finding suggested that the properties of interface layer should be taken into account in order to accurately simulate the J–V characteristics of such heterojunctions. 相似文献
2.
《Journal of magnetism and magnetic materials》2001,237(1):41-46
The structural and magnetic ordering in La0.6Ca0.4MnO3 has been studied by neutron powder diffraction as a function of temperature between 15 and 300 K. The para-ferromagnetic transition at T∼250 K is accompanied by significant structural distortions in the form of octahedral Mn–O6 rotations. At 15 K, the total refined ferromagnetic moment on the Mn site was obtained as 3.1 μB, in reasonable agreement with the total expected average moment of mixed Mn3+/Mn4+ matrix. 相似文献
3.
Hole-doped rare-earth manganite La0.7Ca0.3MnO3 and the electron-doped manganite La0.7Ce0.3MnO3 both show a metal-insulator transition around 250 K associated with a ferromagnetic transition and colossal magnetoresistance.
In an earlier publication we have reported the rectifying characteristic of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction at room temperature, showing that it is possible to fabricate a diode out of the polaronic insulator regime
of doped manganites. Here we report the magneto-transport properties of such a tunnel junction above and below the metal-insulator
transition. We show, from the large positive magnetoresistance of the tunnel junction at low temperature, that La0.7Ce0.3MnO3 could be a minority spin carrier ferromagnet. The implication of this observation is discussed. 相似文献
4.
5.
利用固相反应法制备Pr0.5Ca0.5MnO3(PCMO)靶材,并采用脉冲激光沉积法(PLD)在n型Si(111)基片上沉积PCMO外延薄膜,研究了薄膜的输运特性及薄膜与Si衬底形成异质结的整流特性.结果表明:在80—300 K温度范围内,PCMO薄膜的阻温关系符合变程跳跃模型,随着温度的升高表现出从一维到二维再到三维的转变,分析认为可能源于轨道自由度对电子输运特性的影响.PCMO/Si异质结在磁场作用下整流特性得到改善,且在正向电流方向出
关键词:
0.5Ca0.5MnO3')" href="#">Pr0.5Ca0.5MnO3
Si
整流
正磁电阻 相似文献
6.
The electronic structure of doped orthorhombic (La0.6Pr0.4)0.7Ca0.3MnO3 manganite is studied using the second optical harmonic generation method. The analysis of the frequency and polarization dependence of the intensity related to the second harmonic demonstrates that the applied magnetic field stimulates a transition of spin-polarized electrons from the d orbitals of Mn ions to the p orbitals of O2 ligands. The manifestation of such transition in the orthorhombic RMnO3 manganite with the distorted crystal lattice is attributed to the dipole-forbidden electronic transitions arising in the applied magnetic field. The mechanism of magnetooptical activity induced by the charge transfer between Mn and O ions is discussed. 相似文献
7.
8.
Bibes M Balcells L Valencia S Fontcuberta J Wojcik M Jedryka E Nadolski S 《Physical review letters》2001,87(6):067210
55Mn nuclear magnetic resonance experiments are reported on a series of fully strained epitaxial La(2/3)Ca(1/3)MnO3 thin films on SrTiO3. We have found evidence of multiple phase segregation into ferromagnetic metallic and nonmetallic regions as well as regions that are nonferromagnetic and insulating. These insulating regions are mainly located close to interfaces and may have a significant impact on the performance of spin-tunnel devices. As a result of phase segregation, the ferromagnetic coupling within the metallic regions is depressed. This accounts for the reduction of the Curie temperature and conductivity in nanometric thin films. 相似文献
9.
We have grown La1.48Nd0.4Sr0.12CuO4/La0.67Sr0.33MnO3 (LNSCO/LSMO) bilayer structure on SrTiO3 (0 0 1) substrate. Both temperature dependences of resistivity and magnetization curves show anomalies between 60 < T < 80 K, where a low-temperature orthorhombic (LTO) to low-temperature tetragonal (LTT) structural transition is observed in LNSCO bulk crystal. It is suggested that the formation of domains in LSMO layer can relax the strains caused by the LTO–LTT transition in LNSCO layer. 相似文献
10.
It has been known that bulk La0.6Ca0.4MnO3 is an intermediate material of the first- and second-order characters with the tricritical-point exponents, and the doping of a metal ion in it usually causes a continuous second-order transition. The present work reports the re-entrance of a discontinuous first-order transition in orthorhombic La0.6-xYxCa0.4MnO3 (x = 0.03–0.09) compounds. This enhances the magnetocaloric effect. For the field H = 30 kOe, the maximum magnetic-entropy change (|ΔSmax|) and relative cooling power (RCP) have been evaluated being about 5.45–6.3 J/kg·K and 130–185 J/kg, respectively. If combining these compounds as refrigerant blocks in a rotary ring model, a magnetic cooling device can operate at temperatures T = 85–280 K, with |ΔSmax| ≈ 5.5 J/kg⋅K and RCP ≈ 1073 J/kg. Aside from the re-entranced first-order phase transition, the magnetization and structural analyses have proved the enhanced magnetocaloric effect in La0.6-xYxCa0.4MnO3 related to a Griffiths singularity, and local Jahn-Teller distortions of the perovskite structure (since the Mn3+/Mn4+ ratio and orthorhombic structural phase are unchanged vs. x). 相似文献
11.
Yunqi Cai Ji Ma Qi Cui Wenzhang Wang Hui Zhang Qingming Chen 《Applied Physics A: Materials Science & Processing》2014,117(4):2051-2055
La2/3Ca1/3MnO3 polycrystalline ceramics were synthesized by sol–gel method. Sharp temperature coefficient of resistance (TCR) variation (with peak value up to 22 %) has been observed near the metal-insulator transition temperature T MI (273 K) for the sample sintered at 1,450 °C. This TCR value is much higher than the previously reported values for the undoped and Ag-doped La0.67Ca0.33MnO3 samples and is comparable to the optimized thin films. It was concluded that the improved physical properties of the La0.67Ca0.33MnO3 material are due to its improved microstructure and homogeneity. 相似文献
12.
Epitaxial La0.2Nd0.4Ca0.4MnO3 thin films have been deposited at 800°C on LaAlO3 substrate using pulsed laser deposition technique. The structural and magnetotransport properties of the films have been
studied. The sharp peak in the temperature dependence of the resistance corresponding to metal-to-insulator transition (T
p) has been observed at a temperature of T
p=82 K, 97 K and 110 K for 0 Oe, 20 kOe and 40 kOe magnetic fields, respectively. The film exhibits a large nearly temperature-independent
magnetoresistance around 99% in the temperature regime below T
p. The zero field-cooled (ZFC) and field-cooled (FC) magnetization data at 50 Oe shows irreversibility between the ZFC and
FC close to the ferromagnetic transition temperature T
c=250 K. The ZFC temperature data of the film displays ferromagnetic behavior for higher temperature regime T
c=250 K>T>T
p=82 K, and a decrease in magnetization with decreasing temperature up to 5 K below 82 K exhibiting a sort of antiferromagnetic
behavior in the low temperature regime (T<82 K=T
p=T
N). 相似文献
13.
Dielectric relaxations,magnetodielectric and magnetoelectric interactions in Bi0.6La0.4MnO3 ceramics
A. V. Turik A. V. Pavlenko A. V. Makhiboroda L. A. Reznichenko 《Physics of the Solid State》2016,58(1):97-101
Complex permittivity ε*/ε0 = ε′/ε0–iε″/ε0 of the bismuth–lanthanum manganite Bi0.6La0.4MnO3 ceramics has been measured in the temperature range of 10–220 K at frequencies f = 20–106 Hz and magnetic inductions B = 0–0.846 T. At a temperature of 80 K, the spectra ε′/ε0(t) and ε″/ε0(t) demonstrate the dielectric relaxation that is a superposition of contributions of several relaxation processes, each of which is dominant in its frequency range: I (f < 103 Hz, II (103 < f < 105 Hz), and III (105 < f < 106 Hz). In the range of 10–120 K, anomalous behavior of ε′/ε0(T) and ε″/ε0(T) is observed near the temperature of the transition from the paramagnetic to ferromagnetic phase and is due to the Anderson localization of charge carrier on a spin disorder. 相似文献
14.
The 0.6(Bi1-xLax)FeO 3-0.4SrTiO 3(x = 0,0.1) multiferroic ceramics are prepared by a modified Pechini method to study the effect of substitution of SrTiO3 and La in BiFeO3.The X-ray diffraction patterns confirm the single phase characteristics of all the compositions each with a rhombohedral structure.The magnetic properties of the ceramics are significantly improved by a solid solution with SrTiO3 and substitution of La.The values of the dielectric constant ε r and loss tangent tan δ of all the samples decrease with increasing frequency and become constant at room temperature.The La-doped 0.6BiFeO3-0.4SrTiO3 ceramics exhibit improved dielectric and ferroelectric properties,with higher dielectric constant enhanced remnant polarization(Pr) and lower leakage current at room temperature.Compared with a anti-ferromagnetic BiFeO3 compound,the 0.6(Bi0.9La0.1)FeO3-0.4SrTiO3 sample shows the optimal ferromagnetism with remnant magnetization M r ~ 0.135 emμ/g and ferroelectricity with Pr ~ 5.94 μC/cm 2 at room temperature. 相似文献
15.
16.
A. I. Abramovich L. I. Koroleva Yu. V. Dolzhenkova R. Shimchak 《Physics of the Solid State》2014,56(3):496-500
Spontaneous generation of the electrical voltage in a Pr0.6Ca0.4MnO3 single crystal has been found. The charge and orbital ordering in the crystal takes place at T CO = 240 K, while the antiferromagnetic ordering occurs at T N = 174 K. As the temperature lowers, spontaneous voltage U increases initially slowly (in the temperature range from 300 K to T CO) and then more rapidly (in the range T CO-T N ). Starting from T N , the voltage U increases exponentially and, at 85 K, reaches 115 mV (in the ab plane) and 6.5 mV (along the c axis). The magnetic field differently affects the voltage U in different temperature ranges: it decreases the value of U in the temperature range of 85–130 K and increases in the range of 130–240 K. It is assumed that the spontaneous voltage is associated with the existence of ferromagnetic and charge orbital ordered clusters of different topologies in the crystal. 相似文献
17.
Mahmoud Aly Hamad 《Phase Transitions》2013,86(1-2):106-112
The dependence of magnetization on the variation of temperature for La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 perovskite-type ceramic materials under an external magnetic field was modelled. Application of phenomenological model was performed, showing a good agreement with the experimental data. Temperature dependence of change of both magnetic entropy and specific heat under magnetic field 0.05?T was predicted for La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3. Predicted values of maximum magnetic entropy change, full-width at half-maximum, relative cooling power and maximum specific heat under 0.05 T were evaluated. 相似文献
18.
19.
Leng Liao Kui-juan Jin Hui-bin Lu Peng Han Meng He Guo-zhen Yang 《Solid State Communications》2009,149(23-24):915-918
The dynamic process of photoelectric effects in the La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 heterostructure is theoretically revealed by solving equations consisting of time dependent drift–diffusion, Richardson thermionic emission current, and Shockley–Read–Hall recombination. The calculated time dependent evolution of photovoltage and the variation of carrier concentration are obtained. Present results indicate that a smaller parallel resistance should result in faster photoelectric response, but reduce the peak value of the photovoltage in a La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 heterojunction. In addition, the increase of the carrier mobilities induced by applying higher energy photons can decrease the rise time but increase the peak value of the photovoltage. 相似文献
20.