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研究了半掺杂相分离锰氧化物Eu0.5Sr0.5MnO3样品的结构和电磁输运特性.在半掺杂情况下,该样品呈O′型正交结构,表明样品存在典型的Jahn-Teller畸变;在75 K附近样品的顺磁/反铁磁背景中开始出现铁磁相,在更低的温度42 K,4000 A/m磁场下M-T的场冷曲线和零场冷曲线出现明显分岔,样品的交流磁化率实部随温度的变化曲线中也在42 K观察到尖峰的出现,表现出团簇玻璃行为.在无外加磁场下该样品在
关键词:
多相竞争
半掺杂
铁磁团簇 相似文献
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对Eu1-xSrxMnO3 (x=0.4, 0.5, 0.6, 0.7) 体系的磁结构进行了系统的研究. 通过核磁共振实验, 磁化测量, 并结合电输运测量结果表明, Sr的掺入使得 EuMnO3反铁磁母相中出现铁磁相. 铁磁相和反铁磁相的竞争导致样品在低温下的自旋玻璃行为.分析认为, Eu0.4Sr0.6MnO3和Eu0.3Sr0.7MnO3的磁结构在低温下呈现更加复杂的特征, 主要源于铁磁团簇的形成以及无序相的存在. 相似文献
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本文通过固相反应方法制备了具有钙钛矿结构的稀土掺杂锰氧化物La0.875Sr0.125MnO3(LSMO)块材,并用磁控溅射方法在LaAlO3衬底上生长了厚度为50nm的单晶薄膜.X射线衍射仪分别对LSMO块材和薄膜材料进行分析,表明薄膜和衬底具有相同的钙钛矿结构;通过研究该薄膜光诱导效应和磁场下输运行为,发现其输运性质明显改变,表明外场改变体系的电子自旋输运特性,引起双交换作用减弱和增强,分别导致电阻率的增加和减小. 相似文献
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对半掺杂氧化钴Pr0.5Sr0.5CoO3在居里温度附近的磁熵变进行了研究。研究表明,磁熵变的最大值依赖于外磁场强度;半高宽也与磁场强度有关;相对制冷能力与磁场强度几乎呈线性关系。另外,在不同的温度和磁场强度下测得的磁熵变能够重新标度为一条普适的曲线。依据该唯象的普适曲线,能够较准确的计算出在不同温度和磁场强度下磁熵变的大小。 相似文献
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采用固相反应法制备了样品La0.7-xGdxSr0.3MnO3(x=0.00,0.20,0.30,0.40,0.50).通过测量样品的M~T曲线,ESR曲线,研究了La0.7-xGdxSrO0.3MnO3,体系中的相分离现象及相分离与CMR之间关系.结果表明:当x=0.30,0.40时,在PM-FM相变区产生相分离,并且磁电阻MR得到增强.研究结果表明:La0.7-xGdx Sr0.3MnO3中的相分离与Gd在A位的占位情况紧密相关,磁电阻MR的增强是在外磁场作用下,铁磁区扩大顺磁区减小引起的. 相似文献
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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41K附近,同时,观察到了存在于该体系中负的磁化异常,表明半掺杂的Sm0.5Ca0.5MnO3基态存在有多种复杂而丰富的磁相互作用之间竞争机制,其研究将为强关联锰氧化物体系物理机理的理解提供丰富的实验资料. 相似文献
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《Journal of magnetism and magnetic materials》2004,279(1):91-102
We present results of an electron paramagnetic resonance (EPR) study of Nd1−xSrxMnO3 with x=0.5 across the paramagnetic to ferromagnetic, insulator to metal transition at 260 K (Tc) and the antiferromagnetic, charge ordering transition (TN=Tco) at 150 K. The results are compared with those on Nd0.45Sr0.55MnO3 which undergoes a transition to a homogeneous A-type antiferromagnetic phase at TN=230 K and on La0.77Ca0.23MnO3 which undergoes a transition to coexisting ferromagnetic metallic and ferromagnetic insulating phases. For x=0.5, the EPR signals below Tc consist of two Lorentzian components attributable to the coexistence of two phases. From the analysis of the temperature dependence of the resonant fields and intensities, we conclude that in the mixed phase ferromagnetic and A-type antiferromagnetic (AFM) phases coexist. The x=0.55 compound shows a single Lorentzian throughout the temperature range. The signal persists for a few degrees below TN. The behaviour of the A-type AFM phase is contrasted with that of the two ferromagnetic phases present in La0.77Ca0.23MnO3. The comparison of behaviour of A-type AFM signal observed in both Nd0.5Sr0.5MnO3 and Nd0.45Sr0.55MnO3 with the two FM phases of La0.77Ca0.23MnO3, vis-à-vis the shift of resonances with respect to the paramagnetic phases and the behaviour of EPR intensity as a function of temperature conclusively prove that the Nd0.5Sr0.5MnO3 undergoes phase separation into A-type AFM and FM phases. 相似文献
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The temperature R(T) and field R(H) dependences of the electrical resistance in the compound Eu0.7
A
0.3MnO3 (A=Ca, Sr) are investigated in the temperature range 4.2–200 K in magnetic fields up to 14 T. Above the antiferromagnetic transition
temperature T
a, the function R(T) is semiconducting in character. Application of a magnetic field H that exceeds a certain critical value H
c changes the character of the function R(T) for Eu0.7Sr0.3MnO3 to metallic (dR/dT>0). For T<T
a and H<H
c a jump in the resistance is observed indicating instability of the electronic state caused by competition between charge
and spin ordering of the Mn ions of different valences.
Fiz. Tverd. Tela (St. Petersburg) 40, 708–712 (April 1998) 相似文献
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Lei Shi Haipeng Yang Shiming Zhou Jiyin Zhao Laifa He Shuangyi Zhao Yuqiao Guo Lin Chen 《Solid State Communications》2010,150(7-8):371-374
The structure, magnetic and electrical transport properties of La0.5Sr0.5MnO3 annealed in different atmosphere have been investigated. No evident change of structural symmetry and the Curie temperature is observed for the samples. The resistivity at zero magnetic field of the samples annealed in air and nitrogen exhibits a metal–insulator transition, while no metal–insulator transition is observed for the sample annealed in oxygen, and for which the resistivity decreases monotonously with increasing temperature. Surprisingly, when an external magnetic field is applied, a metal–insulator transition appears for the sample annealed in oxygen. It is suggested that the annealing atmosphere affects the competition between FM and AFM phases due to the change of Mn4+/Mn3+ ratio and the oxygen/cation vacancies, and has a great influence on the electrical transport properties of La0.5Sr0.5MnO3. 相似文献
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F. N. Bukhanko 《Physics of the Solid State》2012,54(6):1199-1206
It has been found that the magnetic susceptibility of (Sm0.5Gd0.5)0.55Sr0.45MnO3 ceramic samples in zero external magnetic field exhibits a sharp peak near the temperature of 48.5 K with a small temperature hysteresis that does not depend on the frequency of measurements and is characteristic of the phase transition to an antiferromagnetic state with a long-range charge orbital ordering, which is accompanied by an increase in the magnetic susceptibility with a decrease in the temperature. The magnetization isotherms in static and pulsed magnetic fields at temperatures below 60 K demonstrate the occurrence of an irreversible metamagnetic transition to a homogeneous ferromagnetic state with a critical transition field independent of the measurement temperature, which, apparently, is associated with the destruction of the insulating state with a long-range charge ordering. In the temperature range 60 K ?? T ?? 150 K, the ceramic samples undergo a magnetic-field-induced reversible phase transition to the ferromagnetic state, which is similar to the metamagnetic transition in the low-temperature phase and is caused by the destruction of local charge/orbital correlations. With an increase in the temperature, the critical transition fields increase almost linearly and the field hysteresis disappears. Near the critical fields of magnetic phase transitions, small ultra-narrow magnetization steps have been revealed in pulsed fields with a high rate of change in the magnetic field of ??400 kOe/??s. 相似文献
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Raman scattering experiments have been carried out on single crystals of Nd0.5Sr0.5MnO3 as a function of temperature in the range of 320–50 K, covering the paramagnetic insulator-ferromagnetic metal transition
at 250 K and the charge-ordering antiferromagnetic transition at 150 K. The diffusive electronic Raman scattering response
is seen in the paramagnetic phase which continue to exist even in the ferromagnetic phase, eventually disappearing below 150
K. We understand the existence of diffusive response in the ferromagnetic phase to the coexistence of the different electronic
phases. The frequency and linewidth of the phonons across the transitions show significant changes, which cannot be accounted
for only by anharmonic interactions. 相似文献
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A. M. Balagurov I. A. Bobrikov V. Yu. Pomjakushin D. V. Sheptyakov N. A. Babushkina O. Yu. Gorbenko M. S. Kartavtseva A. R. Kaul 《Journal of Experimental and Theoretical Physics》2008,106(3):528-541
The results of structural neutron experiments on determining crystal and magnetic phase states of perovskite-like manganites R0.5Sr0.5MnO3 (R = 152Sm, Nd0.772Tb0.228, and Nd0.544Tb0.456) are reported. Experiments are carried out for revealing microscopic factors responsible for the giant oxygen isotope effect that was discovered recently in Sm1?x Sr x MnO3 for x ≈ 0.5. It is shown that separation into two crystal phases P 1 and P 2 with the same spatial symmetry but different types of Jahn-Teller distortions in MnO6 octahedra and magnetic ordering of Mn atoms takes place in all studied compounds at low temperatures. Structural analysis has been carried out successfully owing to exceptionally large differences in the unit cell parameters of the coexisting phases. The P 1 phase is ferromagnetic and MnO6 octahedra are distorted only slightly. The P 2 phase is antiferromagnetic (A-type ordering) and MnO6 octahedra are strongly compressed in the apical direction. The relative volumes occupied by the P 1 and P 2 phases depend on the mean radius of the A cation, and the replacement of 16O by 18O results in their redistribution in favor of the P 2 phase. The results unambiguously point to the percolation nature of the metal-insulator transition in a Sm-containing compound upon isotopic substitution of oxygen due to a sharp decrease (from 65 to 13%) in the fraction of ferromagnetic phase P 1. In all investigated compounds, the ordered magnetic moment of manganese Mn in the P 1 and P 2 phases varies from 1.7μB to 3.5μB. The data on the evolution of the miscrostructure parameters during a phase transition to the stratified state indicate that the initial spread in the A cation radii, as well as the internal microstrains, produce a critical effect on the formation of mesoscopic phase separation. 相似文献