共查询到17条相似文献,搜索用时 99 毫秒
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王芳 《材料科学与工程学报》2007,25(5):785-787
采用固相反应法制备了La0.7Ca0.3MnO3多晶样品并借助X射线衍射,零场下的电阻测量以及电子顺磁共振技术对样品的结构、电子输运和磁性质进行了研究.实验结果表明,在居里温度TC附近,电子顺磁共振(ESR)谱线出现异常,谱线表现出明显的不对称,共振场随着温度的降低向低温方向移动.我们发现在居里温度TC以下用两个洛仑兹峰对ESR谱线可以进行较好的拟合,从而有力地证明了在相转变温度TC附近存在铁磁与顺磁相的共存. 相似文献
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通过系统地测量(La2/3Ca1/3)(Mn(3-x)/3Fex/3)O3(x=0、0.1、0.2、0.3的体系样品的电阻率-温度关系以及一定温度下磁电阻率与磁场的关系,发现随x的变化其磁电阻率峰和电阻率峰均发生位移,磁电阻率峰值增大,并伴生磁电阻率峰展宽效应.作者认为由于Fe的替代,引起体系中Mn3+/Mn4+比率及磁矩的变化,加之外场对磁有序结构的调制作用,从而影响了Mn3+-O-Mn4+的双交换作用,最终导致磁电阻行为发生变化. 相似文献
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制备了Ba缺位型稀土氧化物La0.65BaxMnO3材料,发现随着Ba缺位量在La0.65BaxMnO3中的增加,材料由高晶体对称性向低晶体对称性转移.x>0.30时材料保持立方晶体结构,当x≤0.25时材料呈现菱方晶体结构.在La0.65BaxMnO3中,随Ba成分x从0.35减少到0.33,居里温度有一个小峰,室温电阻率有一小谷;随x进一步减小(x≤0.30),居里温度随之下降,室温电阻率上升.极化子电阻模型分析表明在La0.65BaxMnO3中,电子活动能力(x=0.35)>电子活动能力(x=0.25)>电子活动能力(x=0.20).这与室温电阻率的Ba成分依赖关系吻合.我们还基于迪尼模型计算了La0.65BaxMnO3中电阻随温度的变化关系曲线.计算结果与实验数据符合的较好.计算结果还表明:晶格效应、电-声作用、载流子-晶格(缺陷)耦合作用在解释稀土锰基氧化物材料中的电输运现象方面必须予以考虑. 相似文献
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La2/3Sr1/3MnO3/ZnO混合物薄膜的磁电阻和伏安特性研究 总被引:2,自引:0,他引:2
利用脉冲激光沉积的方法在Si(100)氧化成SiO2的基片上制备了(La2/3Sr1/3MnO3)x/(ZnO)1-x混合物薄膜,研究了薄膜的磁电阻和伏安特性. X射线衍射分析表明,除了衬底SiO2的衍射峰以外,分别出现了La2/3Sr1/3MnO3(101)的衍射峰和ZnO(002)的衍射峰,且它们形成了两相共存体系. 实验表明:x=0.3的混合物薄膜表现为半导体导电特性,而x=0.4的样品则出现了典型的金属绝缘相变. 所制备的样品表现出了低场磁电阻效应和非线性伏安特性. 在0.7T磁场的作用下,x=0.3的样品在温度为60K时取得的最大磁电阻值为28.8%. 通过对伏安关系拟合表明,在La2/3Sr1/3MnO3和ZnO颗粒之间存在一定的耗尽层,且产生了界面缺陷态. 相似文献
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在溶胶-凝胶法制备的La0.47Ba0.38MnO3(LBMO)微粉中掺入CuO粉,制成一系列(LBMO)//(CuO),(x=0.01~0.1,为摩尔比)掺杂材料,实验结果发现.随着Cu掺杂量的增加,材料的磁化强度和居里温度变化不大,材料的电阻率先快速减小,而后缓慢增大,当x=0.01时在全温范围内电阻率都达到最小值,这与Cu离子的价态变化有关。实验还发现Cu离子的掺入可以使材料的室温磁电阻逐步提高.当掺入10%的Cu时,室温磁电阻比达到-8.4%。比未掺杂的LBMO提高了50%。低电阻率导电陶瓷材料和大的室温磁电阻效应都是应用研究所关注的课题。 相似文献
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A. Shengelaya H. Keller K. A. Müller B. I. Kochelaev K. Conder 《Journal of Superconductivity》2000,13(6):955-958
The electron paramegnetic resonance (EPR) of Mn2+ doped into La2–x
Sr
x
CuO4 was used to probe the copper spin relaxation via the bottleneck effect for oxygen isotope (16O and 18O)–substituted samples. It was found that the EPR linewidth is larger for the 18O isotope samples than for the 16O samples. For x = 0.03, the linewidth for the 18O sample is larger than for 16O sample by a factor of 2. The isotope effect is pronounced at low temperatures and decreases with increasing Sr concentration. This effect is quantitatively explained by the Cu2+
S = 1/2 spin relaxation to the lattice via Dzyaloshinski terms coupled linearly to the local Q
4/Q
5 tilting modes of the CuO6 octahedra as proposed by Kochelaev et al. [1] The Q
4/Q
5 modes are coupled sterically to the Q
2 Jahn–Teller modes considered to be relevant for the (bi)-polaron formation and thus for the high-temperature superconductivity (HTSC). 相似文献
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M. R. Gafurov V. A. Ivanshin I. N. Kurkin M. P. Rodionova H. Keller M. Gutmann U. Staub 《Journal of Superconductivity》2000,13(6):895-897
The first observation of electron paramagnetic resonance (EPR) of Tb3+ doped into YBa2Cu3O6 is reported. EPR is used to determine the local symmetry of the rare-earth ion and to study the effect of suppression of high-T
c superconductivity by doping. The distance between the lowest singlets of Tb3+ ion 7.1 GHz 0.24 cm–1 and g-factor g
17.9 have been estimated from measurements. Both these parameters are in a good agreement with the corresponding calculated values. No evidence of Tb4+ ions was found. 相似文献
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采用水热法制备了Ba0.7La0.2Ca0.1TiO3陶瓷材料,研究了MnCO3/MnO2共掺杂对陶瓷材料介电性能的影响及相关的影响规律。随着nMnCO3/nMnO2的增加,材料的介电常数开始增大随后减小,而介电损耗先减小再增大后开始波动,击穿场强先增大后减小。当nMnCO3/nMnO2为3∶1时介电常数最大,得到了介电常数(εr)为4661,介质损耗(tanδ)为0.0165,击穿场强(Eb)为12.58kV/mm,绝缘电阻(R)为3.7×1013Ω的高介电低损耗陶瓷粉体材料。最后探讨了MnCO3/MnO2共掺杂改性的有关机理。 相似文献
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Osami Yanagisawa Mitsuru Izumi Wei-Zhi Hu Kenji Nakanishi Hideo Nojima 《Journal of Superconductivity》1999,12(1):307-310
The magnetic behavior of the distorted perovskite manganese, Pr0.65Ca0.35MnO3 was studied by X-band electron spin resonance for powder samples. We observed the onset of the charge-ordered state at T
CO215 K, the antiferromagnetic transition with the peak of the ESR linewidth, H
p–p
at T
AF180 K and the canted antiferromagnetic transition at T
CAF125 K associated with the abrupt increase of both the effective magnetization and H
p–p
. Below 90 K, the absorption intensity profile becomes weakened with decreasing temperature suggesting the existence of some kind of magnetic disorder below 90 K, which is responsible for a part of evidence of the existence of the spin-glass state as has been proposed by Yoshizawa et al., Phys. Rev. B
52, 1689 (1996). 相似文献