共查询到16条相似文献,搜索用时 265 毫秒
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在La0.67Ca0.33MnO3和La0.67Ba0.33MnO3中用Dy对La进行了置换研究。结果发现,随掺Dy量的增加,两类材料的居里温度和金属-绝缘体相变温度单调下降,峰值电阻率单调增加。在Ca系样品中,掺入13%的Dy后,在5T的磁场下,最大磁电阻比达到7900%。在Ba系样品中.掺Dy对磁电阻的影响要小得多。掺Dy对材料性质的影响可以用晶格效应来解释,但晶格效应产生的作用与碱土离子的品种有明显关系。 相似文献
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将La0.67Sr0.33MnO3(LSMO)、Ag2O及TiO2粉混合经高温烧结后制备了钙钛矿相/xAg两相复合体系(x是Ag与钙钛矿材料的物质的量比),系统地研究了Ag-Ti的共掺杂对LSMO电性和磁电阻效应的影响.0.07摩尔比Ti4+离子的B位掺杂使LSMO的居里温度降至室温.Ag的掺入对Tc影响不大,Tp逐渐升高.由于钙钛矿颗粒属性的改善和金属导电通道的出现,材料的电阻率明显下降.Ag掺杂使室温磁电阻得到显著增强,室温下从x=0.30样品中得到最大的磁电阻,约为32%,是La0.67Sr0.33MnO3样品的8倍,La0.67Sr0.33Mn0.93Ti0.07O3样品的1.6倍. 相似文献
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《功能材料》2012,43(15)
采用脉冲激光沉积法在LaAlO3(LAO)衬底上生长了YBa2Cu3O7/La0.7Ca0.3MnO3(YBCO/LC-MO)和La0.7Ca0.3MnO3/YBa2Cu3O7(LCMO/YBCO)两种外延薄膜,利用高分辨电子显微镜研究了其微观结构。在YBCO/LCMO/LAO薄膜中,LCMO以层-岛模式生长,并形成层状取向畴结构。YBCO层均由c轴取向晶粒组成,其中含有c/3平移畴界、额外CuO层及Y2O3第二相等缺陷结构。在LCMO/YBCO/LAO薄膜中,LAO衬底上初始生长的YBCO为c轴取向,至一定厚度(几个纳米)转为c与a轴混合生长。LCMO层在YBCO上外延生长并具有[100]m与[011]m混合取向畴结构。在LCMO/YBCO界面未观察到失配位错,因此二者界面属应变型界面。 相似文献
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BaoxinHUANC YihuaLIU RuzhenZHANG VouyongDAI ChengjianWANG XiaoboYUAN LiangmoMEI 《材料科学技术学报》2003,19(6):622-624
The representative sample La0.58Dy0.09Ca0.33MnO3 of Dy doped La0.67Ca0.33MnO3 rare-earth manganites was investigated.The most important effect of Dy doping is to introducethe magnetoimpurity and form the spin clusters which induce dramatically large CMR in Lao.58Dyo.09Cao.33MnO3. The fitting results of field-induced resistivity decrease to the Brillouin function indicate that the CMR is caused by the spin dependent hopping between spin clusters. It is the magnetic field that reduces the size of spin clusters and induces a field-induced irreversible CMR behaviour. 相似文献
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La0.67-xCa0.33MnO3系列样品的磁热效应 总被引:4,自引:0,他引:4
用溶胶-凝胶法制备了不同空位浓度掺杂的La0.67-xCa0.33MnO3系列样品(x=0.00,0.02,0.06,0.10),用扫描电子显微镜(SEM)观察了样品的形态和颗粒大小,X射线衍射实验结果显示样品为单相钙钛矿结构,用振动样品磁强计(VSM)测量了样品的磁化强度随温度变化的M-T曲线和起始磁化M-H曲线.研究了空位浓度对样品的居里温度Tc和磁熵变的影响.结果表明,空位浓度的掺杂将样品的居里温度Tc提高至室温附近,磁熵变得到增强.对于经历了一级相变的样品La0.67-xCa0 33MnO3(x=0.02),在居里温度Tc(277 K)附近和1T外磁场下,最大磁熵变达到了2.78 J/(kg·K). 相似文献
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主要就Mn位用不同元素替代对La0.67Ca0.33MnO3磁性、输运行为和磁电阻的影响的实验结果作比较研究,证明Mn位元素替代可能是提高和调制锰氧化物CMR效应的一种有效方法。 相似文献
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采用脉冲激光沉积技术在SnO2:F(FTO)衬底上制备了La0.67 Sr0.33 MnO3( LSMO)薄膜.室温下利用直流电压对Au/LSMO/FTO三明治结构的器件进行了电化学测试.结果显示样品具有明显的双极性电阻开关性能.通过对I-V特性曲线进行分析,认为在高阻态时肖特基势垒和空间电荷限制电流输运机制调控.在高场区,电阻开关的高低阻态现象由电子陷阱中心分布的不对称引起的空间电荷限制电流理论来解释. 相似文献
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Anwar MS Kumar S Ahmed F Kim GW Koo BH 《Journal of nanoscience and nanotechnology》2012,12(7):5523-5526
We report microwave assisted hydrothermal synthesis and magnetocaloric properties of La0.67Sr0.33MnO3 manganite. The synthesized La0.67Sr0.33MnO3 nanoparticles was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and magnetization measurements. The XRD results indicated that La0.67Sr0.33MnO3 nanoparticles have polycrystalline nature with monoclinic structure. FE-SEM results suggested that La0.67Sr0.33MnO3 nanoparticles are assembled into rod like morphology. Magnetization measurements show that La0.67Sr0.33MnO3 nanoparticles exhibit transition temperature (Tc) above room temperature. The maximum magnetic entropy change (deltaS(M))max was found to be 0.52 J/kg K near Tc approximately 325 K at applied magnetc field of 20 kOe. This compound may considered as potential material for magnetic refrigeration near room temperature. 相似文献
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将Bi2O3掺杂到用溶胶—凝胶法制备的La0.6Sr0.33MnO3(LSMO)微粉中,XRD测量结果证实有过量的Bi析出。随着Bi掺杂量的增加,LSMO/(Bi2O3)x/2材料电阻率发生明显变化,在x=(0—0.10)摩尔比的掺杂范围内,电阻率先上升后突然下降。当X=0.1时,电阻率比未掺杂样品下降了一个数量级。Bi掺杂对低温和室温磁电阻有着完全不同的影响。低温下,随掺杂量增加,磁电阻下降;室温下Bi的微量掺杂可以使磁电阻增大,掺入x=0.03Bi使室温磁电阻由-4.4%提高到-5.6%。 相似文献
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Changzhao Chen Bing Wang Xudong Tang Chuanbing Cai 《Journal of Superconductivity and Novel Magnetism》2014,27(7):1683-1688
An elaborately designed bilayer consisting of epitaxial YBa 2Cu 3 O 7?δ (YBCO) and La 0.67Sr 0.33MnO 3?δ (LSMO) films is prepared on a single crystal SrTiO 3 (STO) substrate by pulsed laser deposition (PLD), with respect to the investigation into the influence of spin diffusion on superconductivity. Structural measurements reveal that the present bilayer has good textures of both in-plane and out-of-plane as well as perfect superconducting layer without residual stress. Nevertheless, obviously suppressed superconductivity is found in the bilayer, as evidenced by the reduced superconducting transition temperature and critical current density. It is believed that the suppressed superconductivity arises from the spin diffusion effect due to the comparable length scales of the spin diffusion length and the superconducting film thickness. 相似文献
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用溶胶-凝胶法制备La0.57Ca0.33-0.5xLixMnO3(x=0.00,0.05,0.10,0.20)多晶陶瓷,用XRD分析多晶陶瓷的晶体结构,用SEM对多晶陶瓷的微观形貌进行分析,用标准四探针法测量电阻率-温度关系.结果表明,随着Li掺杂量的增加,所有样品均为斜方晶系,晶胞体积不断减小,金属-绝缘体转变温度(Yp)降低,电阻率不断增加,电阻率温度系数(TCR)不断减小.低温区域(T<TP)的电阻率数据可以用ρ(T)=ρ0+ρ2T2 +ρ4.5T4.5进行拟合;高温区域(T>TP)的电阻率数据可以用小极化子跃迁(SPH)模型和变程跳跃(VRH)模型进行拟合.整个温度区域(100~300 K)可以使用渗透模型对电阻率进行拟合.从拟合数据可知极化子激活能Ea随Li掺杂量的增加而增大,这是由于Li的加入减小了Mn3+-O2--Mn4+的键角,增大了有效带宽的间隙,因此也减弱了双交换作用,增大了电阻率. 相似文献
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