共查询到19条相似文献,搜索用时 93 毫秒
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采用脉冲激光沉积法分别在(100)LaAlO3和(100)SrTiO3基片上生长了La0.33Pr0.34Ca0.33MnO3 薄膜,并通过磁测量和电输运测量对生长在不同基片上的La0.33Pr0.34Ca0.33MnO3薄膜的物性进行了研究.结果表明,基片和薄膜之间的压应力导致La0.33Pr0.34Ca0.33MnO3薄膜容易出现铁磁相,而电荷有序相则被抑制.基片和薄膜之间的张应力则导致La0.33Pr0.34Ca0.33MnO3薄膜容易出现电荷有序相,铁磁相被抑制.导致该现象的可能原因之一是应力使得晶格中Mn-O键角发生改变而引起双交换作用的改变. 相似文献
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采用固相烧结方法制备了Pr1-xCaxMnO3(x=0.3)钙态矿结构锰氧化物陶瓷样品,对其在磁场和电场下的直、交流输运性质做了系统研究.通过测量加磁场和零场下的Ⅰ-Ⅴ曲线,得到其居里温度为150K,与VSM测试结果一致.通过测量加磁场与零场下交流的阻抗频谱,发现加磁场后样品的晶界电阻明显减小,而晶粒电阻几乎保持不变,表明Pr1-xCaxMnO3陶瓷多晶样品的CMR效应源于样品的晶界.为确定晶界处的势垒高度,测量了样品在不同频率下的阻抗温谱,根据Arrhenius定律拟合得出势垒高度为117 meV,与用直流R-T数据拟合得出的激活能一致. 相似文献
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采用高温固态反应法制备了具有钙钛矿结构的锰氧化物La0.67Ca0.33MnO3,利用X射线衍射、超导量子干涉仪等实验技术研究其结构和磁性质。应用标度律对起依赖于磁场的始磁化强度在t→0时的行为用临界指数β随磁场变化进行描述。临界指数β随着磁场的增大而减小,说明在临界点附近,磁场的增大导致自旋有序度的增加。 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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采用脉冲激光沉积技术制备了Ti/Pr0.7Ca0.3MnO3/Pt和Ti/Pr0.7Ca0.3MnO3/La0.67Sr0.33MnO3/Pt异质结并研究了La0.67Sr0.33MnO3功能插层对异质结电致电阻特性的影响. 实验结果表明La0.67Sr0.33MnO3功能层的引入有效提高了器件的电阻转变特性,尤其是电阻转变率和疲劳性得到了极大的改善. 对La0.67Sr0.33MnO3插层改善电致电阻转变特性的机理进行了定性的分析.
关键词:
电致电阻效应
电阻转变比率
疲劳特性 相似文献
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The perovskite bilayers La0.67Ca0.33MnO3 (LCMO) (100 nm) / La0.67Sr0.33MnO3(LSMO) (100 nm) and LSMO (100 nm) / LCMO (100 nm) are fabricated by a facing-target sputtering technique. Their transport and magnetic properties are investigated. It is found that the transport properties between them are different obviously due to distinguishable structures, and the different lattice strains in both films result in the difference of metal-to-insulator transition. Only single-step magnetization loop appears in our bilayers from 5K to 320K, and the coercive force of LSMO/LCMO varies irregularly with a minimum ~ 2387A/m which is lower than that of LCMO and LSMO single layer films. The behaviour is explained by some magnetic coupling. 相似文献
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Ferromagnetic La0.7Sr0.3MnO3 (LSMO) and antiferromagnetic La0.33Ca0.67MnO3 (LCMO) layers were grown on SrTiO3 (STO) substrates by the pulsed laser deposition technique. LSMO films had rougher surfaces and larger grain sizes than LCMO films. Fully strained bilayers, in which each layer was as thin as 10 nm, were prepared by changing their stacking sequences, i.e. LSMO/LCMO/STO and LCMO/LSMO/STO. The former had higher TC (350 K) than the latter (300 K), and exchange bias effects were only observed in the former bilayers. This revealed that microstructures could play an important role in the transport and magnetic properties of manganese oxide thin films. 相似文献
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P.T. Phong N.V. Dai T.D. Thanh L.V. Hong 《Journal of magnetism and magnetic materials》2010,322(18):2737-152
The electrical transport properties and the magnetoresistance of La0.7Ca0.3MnO3/La0.7Sr0.2Ca0.1MnO3 composites are investigated as a function of sintering temperature. On the basis of an analysis by X-ray powder diffraction and scanning electron microscopy we suggest that raising the sintering temperature enhanced the interfacial reaction and creates interfacial phases at the boundaries of the La0.7Ca0.3MnO3 and La0.7Sr0.2Ca0.1MnO3. Results also show that in 3 kOe, and at the Curie temperature, the magnetoresistance value of 14% was observed for the composite sintered at 1300 °C. Based on the phenomenological equation for conductivity under a percolation approach, which depends on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions, we fitted the experimental resistivity—temperature data from 50-300 K and find that the activation barrier decreases as temperature is increased. 相似文献
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A. Rostamnejadi M. VenkatesanP. Kameli H. SalamatiJ.M.D. Coey 《Journal of magnetism and magnetic materials》2011,323(16):2214-2218
The La0.67Sr0.33MnO3 composition prepared by sol-gel synthesis was studied by dc magnetization measurements. A large magnetocaloric effect was inferred over a wide range of temperature around the second-order paramagnetic-ferromagnetic transition. The change of magnetic entropy increases monotonically with increasing magnetic field and reaches the value of 5.15 J/kg K at 370 K for Δμ0H=5 T. The corresponding adiabatic temperature change is 3.3 K. The changes in magnetic entropy and the adiabatic temperature are also significant at moderate magnetic fields. The magnetic field induced change of the specific heat varies with temperature and has maximum variation near the paramagnetic-ferromagnetic transition. The obtained results show that La0.67Sr0.33MnO3 could be considered as a potential candidate for magnetic refrigeration applications above room temperature. 相似文献
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在室温下利用波长532nm,脉冲宽度7ns的纳秒脉冲激光研究了不同电压和激光能量密度作用下Pr0.7Ca0.3MnO3薄膜的瞬态光响应特性.在激光能量密度为275.16mJ/cm2时,其最大电阻变化率达到92.3%,响应时间约36ns.室温下电压变化对薄膜的光响应特性影响不大,而诱导光能量密度的影响则很明显,能量密度越大,电阻变化越大,响应时间越短,并且电阻变化和响应时间均与激光能量密度呈非线性关系.这种光响应来源于薄膜中的光致非稳态绝缘体-金属相变,有望在新型光电器件上获得应用. 相似文献
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Pico-second photoelectric characteristic in manganite oxide La0.67Ca0.33MnO3 films 总被引:1,自引:0,他引:1 下载免费PDF全文
Ultrafast photoelectric characteristic has been observed in La0.67Ca0.33MnO3 films on tilted SrTiO3 substrates. A pico-second (ps) open-circuit photovoltage of the perovskite manganese oxide films has been obtained when the films were irradiated by a 1.064μm laser pulse of 25 ps duration. The rise time and full width at half-maximum of the photovoltage pulse are ~300 ps and ~700 ps, respectively. The photovoltaic sensitivity was as large as ~500 mV/mJ. 相似文献
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Manganite film electrodes were integrated with a spacer layer of strontium titanate to produce an epitaxial La0.67Ca0.33MnO3/(1000 nm)SrTiO3/La0.67Ca0.33MnO3 (LCMO/STO/LCMO) heterostructure by laser ablation. At T = 300 K, the mechanical stresses in the STO layer relaxed to a considerable extent, while the LCMO electrodes were found
to be under biaxial lateral tensile strain, with the lattice unit cell of the top electrode distorted considerably stronger
(a
∥/a
⊥ ≈ 1.026) than that of the bottom electrode (≈1.008) (a
∥ and a
⊥ are the unit cell parameters in the substrate plane and along the normal to its surface, respectively). The reciprocal of
the capacitance C of the plane-parallel LCMO/STO/LCMO film capacitors thus formed increased almost linearly with increasing temperature T in the range 50–250 K. At T < 100 K, the capacitance C decreased by approximately 50% in an electric field E = 40 kV/cm. After the electric field E was varied as 0 → + 100 kV/cm → 0, the capacitance C decreased by approximately 3% and the maximum in the C(E, T > 200 K) dependence shifted by approximately 9 kV/cm with respect to the point E = 0. 相似文献
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Polycrystalline perovskite La0.67Ca0.33MnO3 was synthesized by a sol–gel method. Its adiabatic temperature change ΔTad induced by a magnetic field change was measured directly. At 268 K, near its Curie temperature TC, ΔTad of La0.67Ca0.33MnO3 induced by a magnetic field change of 2.02 T reaches 2.4 K. The latent heat Q and magnetic entropy change −ΔSM induced by a magnetic field change were calculated from the temperature dependence of ΔTad and zero-field heat capacity Cp. The maximum values of Q and −ΔSM in La0.67Ca0.33MnO3 induced by a magnetic field change of 2.02 T are 1.85 J g−1 and 6.9 J kg−1 K−1, respectively. The former is larger than the phase transition latent heat of heating or cooling, which is about 1.70 J g−1. 相似文献