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1.
利用固相反应法制备了Bi0.5Ca0.5Mn1-xCoxO3(0≤x≤0.12)系列多晶样品.研究了Co掺杂对Bi0.5Ca0.5MnO3电荷有序的影响.结果表明,Co掺杂导致电荷有序相逐渐融化、铁磁相互作用的增强;当x≥0.08时,电荷有序转变峰完全消失,但残留的反铁磁电荷有
关键词:
钙钛矿锰氧化物
电荷有序
团簇玻璃
相分离 相似文献
2.
通过对La0.3Ca0.7Mn1-xWxO3(x=0.00,0.04,0.08,0.12,0.15)多晶样品M-T曲线、M-H曲线及ESR谱的测量,研究了Mn位W掺杂对电荷有序体系La0.3Ca0.7MnO3磁结构的影响.结果表明,当掺杂量为0.00≤x≤0.08时,体系存在电荷有序(CO)相,AFM/CO态共存于相变温度以下,电荷有序温度TCO随着W掺杂量的增加而增加;x=0.04时,样品在低温下为FM相与AFM/CO相共存,在CO相建立前、后均有FM从PM中分离出来;当x≥0.12时,CO态融化,在极低温度下存在顺磁-铁磁(PM-FM)相变.
关键词:
磁结构
电荷有序
融化
Mn位掺杂 相似文献
3.
4.
5.
利用固相反应烧结技术制备La0.1Bi0.9-xEuxFeO3系列化合物. 利用X射线粉末衍射进行物相鉴定和结构分析,确定了材料的相关系:x≤0.05,材料为R3c结构相;0.08≤x≤0.12,材料为赝R3c结构相;x≥0.15是Pbnm相,其中0.15≤x≤0.20区域Pbnm相存在畸变. 磁测量结果表明,材料具有弱铁磁性,对于x≤0.20材料,磁矩在x=0.12成分存在极值. 利用阻抗分析仪测量了室温介电常数随成分的变化关系.讨论了材料的结构与弱铁磁性和室温介电常数间的关系.
关键词:
0.1Bi0.9-xEuxFeO3')" href="#">La0.1Bi0.9-xEuxFeO3
X射线衍射
磁性
介电常数 相似文献
6.
本文采用基于密度泛函理论的第一性原理全势能线性缀加平面波方法(FLAPW),分析了Bi2Te3-xSex体系中各原子自旋轨道耦合(SOI)的p1/2修正对体系性质的影响,并对Bi2Te3-xSex(x≤3)同晶化合物的电子特性进行系统的理论研究,首次计算出Bi2S
关键词:
2Te3-xSex(x≤3)同晶化合物')" href="#">Bi2Te3-xSex(x≤3)同晶化合物
第一性原理
电子结构
自旋轨道耦合 相似文献
7.
通过对La2-xNdxCuO4+δ(0.1≤x≤1.2)体系中滞弹性弛豫与相变内耗性能的研究发现,当0.1≤x≤1.0时,在250K左右存在一个与间隙氧有关的弛豫内耗峰,并且当0.1≤x≤0.4时,弛豫内耗峰峰高随着x值的增大而升高,此时体系为正交结构;当0.5≤x≤1.0时,体系在宏观上呈现四方结构,此时内耗峰峰高随着x<
关键词:
2-xNd<i>xCuO4+δ')" href="#">La2-xNd<i>xCuO4+δ
间隙氧
弛豫内耗峰
相变内耗峰 相似文献
8.
研究了半掺杂锰氧化物Sm0.5Ca0.5MnO3体系的结构、输运和磁特性,结果表明,在半掺杂情况下,该体系呈现O′类正交结构,表明体系存在典型的Jahn-Teller效应畸变;输运结果在整个测量温区均呈现半导体导电行为,没有出现金属-绝缘体(M-I)转变和CMR效应;电荷有序转变发生在T=270K左右,反铁磁转变温度出现在200K附近,且表现出典型的再入型自旋玻璃(spin-glass)行为,自旋玻璃转变温度TSG在4
关键词:
自旋玻璃
电荷有序
负磁化现象
多相竞争 相似文献
9.
研究了Nd0.5Ca0.5MnO3体系的结构和输运特性. 结构 分析表明,在300K下,体系表现为O′型正交结构并存在典型的Jahn-Teller畸变.在8 T磁场 下,体系出现顺磁绝缘-铁磁金属的转变,庞磁电阻效应发生. 磁测量发现,样品的奈尔温 度TN和电荷有序转变温度TCO分别在150和240K左右,在41K左右出 现典型再入型自旋玻璃行为,同时观察到了负的磁化率异常. 结果表明,Nd关键词:
庞磁电阻
自旋玻璃态
负磁化强度
电荷有序 相似文献
10.
11.
We report measurements of non-linear charge transport in epitaxial (La1−x
Pr
x
)0.7Ca0.3MnO3 thin films fabricated on (100) oriented SrTiO3 single crystals by pulsed laser deposition. The end members of this series, namely Pr0.7Ca0.3MnO3 and La0.7Ca0.3MnO3 are canonical charge-ordered (CO) and ferromagnetic manganites, respectively. The onset of the CO state in Pr0.7Ca0.3MnO3 is manifested by a pronounced insulating behavior below ∼ 200 K. The CO state remains stable even when a large (∼ 2×105 V/cm) electric field is applied across the thin film samples. However, on substitution of Pr with La, a crossover from the
highly resistive CO state to a state of metallic character is observed at relatively low electric fields. The current-voltage
characteristics of the samples at low temperatures show hysteretic and history dependent effects. The electric field driven
charge transport in the system is modelled on the basis of an inhomogeneous medium consisting of ferromagnetic metallic clusters
dispersed in a CO background. 相似文献
12.
S. M. Yusuf 《Pramana》2004,63(1):133-141
We have investigated magnetic correlations in various CMR manganites on macroscopic, mesoscopic and microscopic length scales
by carrying out DC magnetization, neutron depolarization, and neutron diffraction measurements. We present here the effect
of substituting Mn with Fe and La with Dy in the ferromagnetic La0.7−xCaxMnO3 (x ∼ 0.3–0.33) compounds. Neutron diffraction has been used in order to characterize the long-range magnetic order and its gradual
suppression by the substitution. Neutron depolarization study has been carried out in order to bridge the gap in our understanding
regarding the nature of magnetic correlation obtained from the macroscopic and microscopic measurements. In particular, our
study on La0.67Ca0.33Mn0.9Fe0.1O3 has established the fact that a true double exchange mediated spin-glass is insulating. In another study of La-site ionic
size effect and its disorder in (La1−x
Dy
x
)0.7Ca0.3MnO3, we have investigated the evolution of the length scale of magnetic ordering with a possible microscopic explanation and
the results have been compared with that for the light rare earth substituted compounds. 相似文献
13.
Wei Ning 《Journal of magnetism and magnetic materials》2009,321(2):88-90
Electron spin resonance (ESR) measurements have been performed on polycrystalline samples of Pr1−xCaxMnO3 (x=0.4, 0.5) in the temperature range of 100-300 K. The temperature dependence of ESR intensity, g value and linewidth shows the existence of ferromagnetic spin correlations in the paramagnetic state. With decreasing temperature, the ferromagnetic spin correlations switch to antiferromagnetic spin correlations in the charge ordering state and vanish at the antiferromagnetic ordering temperature TN. 相似文献
14.
《Journal of Physics and Chemistry of Solids》2002,63(6-8):935-937
We have studied the magnetic dilution and electronic nature of Zn doping on the Mn site in the colossal magnetoresistant material La0.7Pb0.3MnO3 (x≤0.3). Small non-magnetic Zn2+ doping tends to separate the system into ferromagnetic clusters to weaken the long-range ferromagnetic order and to reduce the Curie temperature. The spin polarizability of the x=0–0.3 samples is estimated to be 0.97–1.00, indicating that the x=0–0.3 samples are the spin polarized materials in which the conductivity is dominated by single-spin charge carriers. Small doping (x≥0.1) induces the metal–insulator transition and destroys the metallic state with long-range ferromagnetic order. 相似文献
15.
Magnetic properties of Nd0.5Sr0.5Mn1-x(Gax,Tix)O3 system (0.04≤x≤0.4) were investigated through magnetization and electron spin resonance (ESR) measurements. It was observed that a small amount of Ti substitution for Mn will destroy the charge-ordering (CO) phase completely and induce the cluster-spin-glass phase in the system, which displays a procedure of collapse of CO and of an enhancement of spin ordering (SO) phase. In contrast, the Ga substitution for Mn induces a melting of CO phase in the system. It was observed that with substitution the CO phase is suppressed gradually and the remanent CO phase is retained all the while, and withal, there is a co-existence of AFM CO phase and FM SO at low temperature. In addition, an abrupt rise of magnetization was observed in M-Tcurves. We attributed this abnormal phenomenon to a transition from canted AFM SO to FM SO in CO region. 相似文献
16.
Electronic transport properties of La0.5?xBixCa0.5MnO3 (x=0, 1/16, 1/8, 1/4, 3/8 and 1/2) compounds have been studied systematically to investigate their charge ordering (CO) behaviors. The results show that the CO temperature increases with the substitution of Bi3+ ion for La3+ ion, suggesting that the charge ordering is enhanced. This is attributed to the special role of the 6s2 lone pair of Bi3+. It is found that for all the samples the adiabatic small polaronic conduction mechanism is responsible for the transport behavior above CO transition, whereas Mott's variable range hopping mechanism dominates below the CO transition. In addition, the electronic transport behavior of La0.5?xBixCa0.5MnO3 compounds is high sensitive to an external magnetic field, which could raise fresh opportunities for application in magnetic sensors. 相似文献
17.
Anowar Tozri Moez Bejar Essebti Dhahri EL Kébir Hlil 《Central European Journal of Physics》2009,7(1):89-95
X-ray powder diffraction (XRD) and magnetic measurements were performed in order to investigate the effect of Na+ ion substitution for Ca2+ ions on the crystallographic structure, the character of magnetic ordering, and the effect of transition temperature in La0.7Ca0.3−x
Na
x
MnO3 manganites series (0 ⩽ × ⩽ 0.2). All samples crystallise in an orthorhombic structure with the Pnma space group. We have found a strong dependence of structural and magnetic properties on the cation-size disorder parameter
σ
2. The temperature dependence of magnetization of all samples obeys the Bloch T
3/2 law. The values of the spin wave constant at low temperature B increase with the increase of x and the Curie temperature decreases. It is concluded that the substitution of Ca by Na+ ions causes a decrease in total exchange integral Aof the samples.
相似文献