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1.
利用脉冲激光沉积方法在Si(100)上制备了Cox-C1-x颗粒膜,并研究了其正磁电阻效应.实验结果表明,样品在室温下的正磁电阻效应要远远高于低温下的正磁电阻效应;Co0.02-C0.98样品具有最大的室温正磁电阻效应,在外加磁场B=1T时,其磁电阻率MR=22%;随着Co含量的增加,Cox-C1-x颗粒膜的正磁电阻效应呈减小趋势.样品的MR-B的曲线与传统的多层膜及颗粒膜结构有很大的不同,这一现象表明在实验样品中可能存在着一种新的输运机制. 相似文献
2.
一种新的庞磁电阻氧化物薄膜La1-xPrxMnO3(x=0.1,0 .2)薄膜用脉冲激光沉积(PLD)方法生长在(100)SrTiO3单晶基底上.XRD结果显示 薄膜具有很好的外延单晶取向.电输运和磁性质的研究表明薄膜具有显著的庞磁电阻效应(CM R)效应,其中磁电阻比率达95%(在5T的磁场下).X射线光电子能谱(XPS)的结果表明薄膜体 系中Pr离子的价态为+4价,因此该薄膜很可能是电子掺杂的庞磁电阻体系.
关键词:
脉冲激光沉积
1-xPrxMnO3')" href="#">La1-xPrxMnO3
电子 掺杂
庞磁电阻 相似文献
3.
利用固相反应法在700℃—1000℃不同的温度下、空气中烧结Co3O4 和TiO2混合物,制备了(Co3O4)x/3(TiO2)1-x(03,说明Co3O4与TiO2反应形成了CoT iO3;同时,在700 ℃低温和900 ℃以上的高温烧结样品中分别观察到了单相的 锐钛矿和金红石相结构.经高低温烧结的样品在500 ℃氢退火后,CoTiO3相消失 ,锐钛矿相的CoxTi1-xO2-δ形成.X射线光电子能谱(X PS)分析显示,氢退火样品中的Co以+2氧化价态存在,同时没有观察到金属态的Co,这说明 氢退火样品中的室温铁磁性不是源于金属Co颗粒的形成,而是与钙钛矿结构的CoTiO3< /sub>相的消失和锐钛矿型的CoxTi1-xO2-δ相的形成 有关.(Co3O4)x/3(TiO2)1-x( 0x Ti1-xO2-δ相的本征铁磁性,伴随着结构相变而产生的Co离子之间的铁磁交换相互作用或 许是样品室温铁磁性产生的根本原因.
关键词:
室温铁磁性
结构相变
锐钛矿
氢退火 相似文献
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在成功制备具有双钙钛矿结构Sr2Fe1-xCoxMoO6系列样品的基础上,对其结构、输运性质和磁性质进行了系统研究.结果发现,随着Co替代浓度x值的增加,样品的电阻率-温度关系由半金属行为转变为半导体行为,其室温电阻率从3.9×10-5Ω·cm增大到6.0×10-1Ω·cm;样品由亚铁磁体转变成反铁磁体,其磁相变温度TN值也随之下降; Co对Fe的部分替代使其磁电阻效应受到抑制.基于对其电子结构的分析,其磁电阻效应的起源以及Co的元素替代效应也在文中进行了讨论.
关键词:
双钙钛矿结构
2FeMoO6')" href="#">Sr2FeMoO6
磁电阻 相似文献
6.
用溶胶-凝胶方法制备了1/mAg2O-La0.833K0.167MnO3 (LKMO/Ag)系列样品,其中1/m代表Ag2O和La0.833K0.167MnO3(LKMO)的摩尔比,m=32,16,8,4和2. 研究了此系列样品的结构、磁性和输运特性. X射线衍射实验表明,LKMO/Ag是一个非均匀的系统,样品由磁性的钙钛矿相LKMO和金属Ag相组成. 由于Ag相的加入,在室温条件下,磁电阻效应明显增强. 在300 K, 0.5 T磁场下,m=4样品的磁电阻可以达到32%;5.5 T磁场下,其磁电阻可达64%. 而单纯的LKMO样品在相同条件下的磁电阻分别为10%和35%. 在低温下,加Ag样品的磁电阻效应反而减小,样品含Ag越多,磁电阻效应越小. 用非本征磁电阻(包括自旋极化隧穿和自旋相关散射)和本征磁电阻在不同温区对总磁电阻的相对贡献对此系列样品的磁电阻现象作了定性的解释.
关键词:
自旋极化隧穿
自旋相关散射
低场磁电阻
高场磁电阻 相似文献
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研究了溶胶-凝胶法制备氧化物巨磁电阻材料的工艺,制备了La0.7Sr0.3< /sub>CrxMn1-xO3(x=0,0.10,0.15)和La0.7Sr0.3FexMn1-xO3(x=0.05,0.10,0.16)两 系列的单相钙钛矿锰氧化物多晶样品,并研究了Cr,Fe替代La0.7Sr0.3 sub>MnO3中部分Mn后对其结构、磁性和巨磁电阻性质的影响.观察到La0.7 Sr0.3Cr0.15Mn0.85O3和La0. 7Sr0.3Fe0.05Mn0.95O3两个样品的 电阻-温度曲线都出现了双峰.定性讨论了可能产生双峰的机制.随Cr(或Fe)替代量的增加, 材料的居里温度很快下降,铁磁性减弱,导电性降低,巨磁电阻效应增强.但与Fe掺杂相比 ,相同数量的Cr掺杂对材料的影响要小.
关键词:
巨磁电阻效应
溶胶-凝胶工艺
电阻-温度曲线
金属绝缘体转变 相似文献
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采用基于第一性原理的密度泛函理论全势线性缀加平面波法,使用广义梯度近似处理交换相关势能,首先计算了β-FeSi2的电子结构及其各元素各亚层电子的能态密度,β-FeSi2的电子能态密度主要由Fe的d层电子和Si的p层电子的能态密度确定;其次通过计算不同掺杂系统的总能量确定了掺杂原子在β-FeSi2中的置换位置,在β-FeSi2中,Co置换FeⅡ位置的Fe原子,Al置换SiⅠ位置的Si原子,这种择位置换与现有的计算结果完全一致;最后计算了Fe1-xCoxSi2和Fe(Si1-xAlx)2的电子结构,对它们的电子结构特征进行了分析,并探讨了电子结构对其热电性能(塞贝克系数、电传输及热传输性能)的影响.
关键词:
第一性原理
电子结构
热电性能
2')" href="#">FeSi2 相似文献
13.
The crystal structure and the superconductivity for samples Mg(B1-xCx)2 (0〈 x 〈0.09) prepared by a hybrid microwave synthesis have been investigated. The starting material B10C is also obtained by using the microwave method. The carbon can distribute uniformly in the Mg(B1-xCx)2 samples because boron and carbon are mixed on an atomic scale in the staring material B10C. The dependences of both lattice parameters and superconducting transition temperature Tc on carbon content accord with those reported in the literature. The upper critical field He2 at 20 K can be enhanced from about 4.3 T for x = 0 to 10 T for x = 0.05. The critical current density Jc of Mg(B0.95 C0.05)2 is 1.05×10^4 A/cm^2 at 20 K and 1 T. 相似文献
14.
Preparation, structure and ferromagnetic properties of the nanocrystalline Ti1-xMnxO2 thin films grown by radio frequency magnetron co-sputtering
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This paper reported that the Mn-doped TiO2 films were prepared by radio frequency (RF) magnetron cosputtering. X-ray diffraction measurements indicate that the samples are easy to form the futile structure, and the sizes of the crystal grains grow big and big as the Mn concentration increases. X-ray photoemlssion spectroscopy measurements and high resolution transmission electron microscope photographs confirm that the manganese ions have been effectively doped into the TiO2 crystal when the Mn concentration is lower than 21%. The magnetic property measurements show that the Ti1-xMnxO2 (x = 0.21) films are ferromagnetic at room temperature, and the saturation magnetization, coercivity, and saturation field are 16.0 emu/cm^3, 167.5 × 80 A/m and 3740 × 80 A/m at room temperature, respectively. The room-temperature ferromagnetism of the films can be attributed to the new futile Ti1-xMnxO2 structure formed by the substitution of Mn^4+ for Ti^4+ into the TiO2 crystal .lattice, and could be explained by O vacancy (Vo)-enhanced ferromagnetism model. 相似文献
15.
室温下在单晶Si中注入(0.6—1.5)at%的C原子,部分样品在C离子注入之前在其中注入29Si+离子产生损伤,然后在相同条件下利用高温退火固相外延了Si1-xCx合金,研究了预注入对Si1-xCx合金形成的影响.如果注入C离子的剂量小于引起Si非晶化的剂量,在950℃退火过程中注入产生的损伤缺陷容易与C原子结合形成缺陷团簇,难于形成Si1-xC关键词:
离子注入
固相外延
1-xCx合金')" href="#">Si1-xCx合金 相似文献
16.
The magnetic properties of (Cox Fe1-x)A (Zn1-x Fe1+x)B O4 are studied using mean-field theory and the probability distribution law to obtain the saturation magnetization, the coercive field, the critical temperature, and the exchange interactions with different values of D (nm) and x. High-temperature series expansions (HTSEs) combined with the Pade approximant are used to calculate the critical temperature of (CoxFe1-x)A(Znl-xFe1+x)BO4, and the critical exponent associated with magnetic susceptibility is obtained. 相似文献
17.
Composition-induced structural modifications in the quaternary CuIn1-xGaxSe2 thin films: bond properties versus Ga content
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In this paper the dependence of structural properties of the quaternary CuIn1-xGaxSe2 films with tetragonal structure on the Ga content has been systematically investigated by Raman scattering and x-ray diffraction spectra. The shift of the dominant A1 mode, unlike the lattice constants, does not follow the linear Vegard law with increasing Ga content x, whereas exhibits approximately polynomial change from 174 cm^-1 for CuInSe2 to 185 cm^-1 for CuGaSe2. Such behaviour should be indicative of presence of the asymmetric distribution of Ga and In on a microscopic scale in the films, due to Ga addition. The changes in the tetragonal distortion η lead to a significant variation in the anion displacement parameter U, which should be responsible for the evolution of bond parameters and resultant Raman bands with x. 相似文献
18.
19.
Photoluminescence and transmission spectra of nanocrystalline GaAs(1-x)Sbx embedded in silica films
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The composite films of the nanocrystMline GaAs(1-x)Sbx-SiO2 have been successfully deposited on glass and GaSb substrates by radio frequency magnetron co-sputtering. The 10K photoluminescence (PL) properties of the nanocrystalline GaAs(1-x)Sbx indicated that the PL peaks of the GaAs(1-x)Sbx nanocrystals follow the quantum confinement model very closely. Optical transmittance spectra showed that there is a large blue shift of optical absorption edge in nanocrystMline GaAs(1-x)Sbx-SiO2 composite films, as compared with that of the corresponding bulk semiconductor, which is due to the quantum confinement effect. 相似文献
20.
MgxZn1-xO thin films have been prepared on silicon substrates by radio
frequency magnetron sputtering at 60℃. The thin films have hexagonal
wurtzite single-phase structure and a preferred orientation with the c-axis
perpendicular to the substrates. The refractive indices of MgxZn1-xO films
are studied at room temperature by spectroscopic ellipsometry over the wavelength
range of 400--760\,nm at the incident angle of 70℃. Both absorption
coefficients and optical band gaps of MgxZn1-xO films are determined by
the transmittance spectra. While Mg content is increasing, the absorption edges of
MgxZn1-xO films shift to higher energies and band gaps linearly increase
from 3.24.eV at x=0 to 3.90\,eV at x=0.30. These results provide important
information for the design and modelling of ZnO/ MgxZn1-xO heterostructure
optoelectronic devices. 相似文献