A general consideration is presented for the magnetic interaction at an interface between a perovskite manganite and other transition metal oxides. The latter is specified by the electron number $n$ in the $d_{3z^2-r^2}$ level as $(d_{3z^2-r^2})^n$. Based on the molecular orbitals formed at the interface and the generalized Hund's rule, the sign of the magnetic interaction is rather uniquely determined. The exception is when the $d_{3z^2-r^2}$ orbital is stabilized in the interfacial manganite layer neighboring to a $(d_{3z^2-r^2})^1$ or $(d_{3z^2-r^2})^2$ system. In this case, the magnetic interaction is sensitive to the occupancy of the Mn $d_{3z^2-r2}$ orbital. It is also shown that the magnetic interaction between the interfacial Mn layer and the bulk region can be changed. Manganite-based heterostructures thus show a rich magnetic behavior. We also present how to generalize the argument including $t_{2g}$ orbitals.
The present work theoretically studies the possibility to hinder the formation of a "dead" layer at the interfaces in manganite superlattices. We showed that this goal can be reached by using alkaline-earth simple oxides as alternating layers in very thin superlattices. Indeed, such alternating layer promotes the contraction of manganite layers at the interfaces and $d_{x^2-y^2}$ preferred $e_g$ orbital occupancy, while Boltzman's transport calculations show an increase in conductivity. This result hold for different manganites, different alkaline-earth simple oxides as well as different thick…
In this work we studied the influence of particle size and agglomeration in the performance of solid oxide fuel cell cathodes made with nanoparticles of La0.8Sr0.2MnO3. We followed two synthesis routes based on the Liquid Mix method. In both procedures we introduced additional reagents in order to separated the manganite particles. We evaluated cathodic performance by Electrochemical Impedance Spectroscopy in symmetrical (CATHODE/ELECTROLYTE/CATHODE) cells. Particle size was tuned by the temperature used for cathode sintering. Our results show that deagglomeration of the particles, serves to i…
Interface-dominated materials such as nanocrystalline thin films have emerged as an enthralling class of materials able to engineer functional properties of transition metal oxides widely used in energy and information technologies. In particular, it has been proved that strain-induced defects in grain boundaries of manganites deeply impact their functional properties by boosting their oxygen mass transport while abating their electronic and magnetic order. In this work, the origin of these dramatic changes is correlated for the first time with strong modifications of the anionic and cationic …
The introduction of manganite buffer layers, La7/8Sr1/8MnO3 (LSMO) in particular, at the metallic interface between SrTiO3 (STO) and another band insulator suppresses the carrier density of the interfacial two-dimensional electron gas (2DEG) and improves significantly the electron mobility. However, the mechanisms underlying the extreme mobility enhancement remain elusive. Herein, we used 18O isotope exchanged SrTi18O3 as substrates to create 2DEG at room temperature with and without the LSMO buffer layer. By mapping the oxygen profile across the interface between STO18 and disordered LaAlO3 o…
We report on the growth and characterization of Ti/$La_{1/3}$$Ca_{2/3}$Mn$O_3$/Si$O_x$/n-Si memristive devices. We demonstrate that using current as electrical stimulus unveils an intermediate resistance state, in addition to the usual high and low resistance states that are observed in standard voltage controlled experiments. Based on thorough electrical characterization (impedance spectroscopy, current-voltage curves analysis), we disclose the contribution of three different microscopic regions of the device to the transport properties: an ohmic incomplete metallic filament, a thin manganite…
The breaking of orbital degeneracy on a transition metal cation and the resulting unequal electronic occupations of these orbitals provide a powerful lever over electron density and spin ordering in metal oxides. Here, we show how to dynamically modulate the orbital populations on Mn atoms at ferroelectric/manganite interfaces by switching the ferroelectric polarization. The change in orbital occupation can be as large as 10\%, greatly exceeding that of bulk manganites. This flippable orbital splitting is in large part controlled by the propagation of ferroelectric polar displacements into the…
We show evidence that the competition between the antiferromagetic metallic phase and the charge- and orbital-ordered insulating phase at the reentrant phase boundary of a layered manganite, LaSr2Mn2O7, can be manipulated using ultrafast optical excitation. The time-dependent evolution of the Jahn-Teller superlattice reflection, which indicates the formation of the charge and orbital order, was measured at different laser fluences. The laser-induced enhancement and reduction the Jahn-Teller reflection intensity shows a reversal of sign between earlier (~10 ns) and later (~150 ns) time delays d…
Manipulation of oxygen vacancies (V_O) in single oxide layers by varying the electric field can result in significant modulation of the ground state. However, in many oxide multilayers with strong application potentials, e.g. ferroelectric tunnel junctions and solid-oxide fuel cells, understanding V_O behaviour in various layers under an applied electric field remains a challenge, owing to complex V_O transport between different layers. By sweeping the external voltage, a reversible manipulation of V_O and a corresponding fixed magnetic phase transition sequence in cobaltite/manganite (SrCoO3-…
The breaking of orbital degeneracy on a transition metal cation and the resulting unequal electronic occupations of these orbitals provide a powerful lever over electron density and spin ordering inmetal oxides. Here, we use ab initio calculations to show that reversibly modulating the orbital populations on Mn atoms can be achieved at ferroelectric/manganite interfaces by the presence of ferroelectric polarization on the nanoscale. The change in orbital occupation can be as large as 10%, greatly exceeding that of bulk manganites. This reversible orbital splitting is in large part controlled b…
Lanthanum manganite, LaMnO (LMO) is the parent compound for a class of hole doped(e.g. La1-xCaxMnO3, La1-xSrxMnO3) and electron doped (e.g. . La1-xCexMnO3, La1-xSnxMnO3) perovskite complex oxide materials. Strong correlation between the spin,lattice, charge and orbital degrees of freedom is a hallmark of these class of materials (popularly known as manganites). Competition and interplay of these degrees of freedom lead to a wide range of interesting electronic behavior including half-metallicity, colossal magneto-resistivity, etc. Although a lot of experimental research has been carried out on…
Metal-insulator transition and electroresistance in lanthanum/calcium manganites La_<1-x>Ca_<x>MnO_<3> (x = 0-0.5) from voltage-current-temperature surfaces
Observation of 300 K High Energy MagnetoDielectric Response in the Bilayer Manganite (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$
我们在双层锰氧化物（La $_{0.4}$ Pr $_{0.6}$）$_{1.2}$ Sr $_{1.8}$ Mn $_2$ O $_7$中观察到大的HEMD效应，这是场驱动的自旋玻璃绝缘体到铁磁金属转变的直接结果。过渡的残余物可用于在室温下实现介电对比度。这一发现表明，电子机制，如金属-绝缘体转变，电荷排序，和轨道排序，可以利用在其他材料中提供实质性的介电对比度。
Competition between covalent bonding and charge transfer at complex-oxide interfaces
在这里，我们研究了铜酸盐/锰氧化物界面的电子性质。利用原子分辨电子显微镜和能谱技术，我们制作了一幅亚纳米尺度的过渡金属氧化态分布图，它位于高$T_c$超导体YBa $_2$ Cu $_3$ O $_{7-δ}$和巨磁电阻化合物（La，Ca）MnO $_3$之间的界面上.电子从锰氧化物到铜氧化物的净转移具有特殊的非单调电荷分布。模型计算合理化的配置文件之间的竞争标准的电荷转移趋势（由于带失配），强化学键合效应的界面，和Cu取代到Mn晶格，具有不同的特征长度尺度。
Reentrant metallic transition at a temperature above Tc at the breakdown of cooperative Jahn-Teller orbital order in perovskite manganites
我们报告了一个有趣的重入金属电阻率图案超过一个特征温度T*，这是高于其他这样的特征转变温度，如T（c）（居里点），T（N）（Neel点），T（CO）（充电顺序开始点）或T（OO）（轨道序起始点）在稀土钙钛矿锰氧化物（RE（1-x）A（x）MnO（3）; RE = La，Nd，Y; A = Sr，Ca; x = 0.0-0.5）范围内。这种行为通常在掺杂水平（x）高于出现金属基态所需的临界掺杂水平x（c）（= 0.17-0.22）的掺杂锰氧化物中观察到，因此在合作的Jahn-Teller轨道序已经发生击穿的系统中观察到。然而，在La（1-x）Ca（x）MnO（3）（x = 0.0-0.5）系列中所做的观察结果证明是这种总趋势的例外。
Resistive relaxation in field-induced insulator-metal transition of a (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ bilayer manganite single crystal
研究了（La $_{0.4}$ Pr $_{0.6}$）$_{1.2}$ Sr $_{1.8}$ Mn $_{2}$ O $_{7}$单晶的电阻弛豫，以考察双层锰氧化物场致绝缘体-金属转变的慢动力学.在recrystalline电阻中观察到的时间分布遵循拉伸指数函数，伴随着类似于在磁化和磁致伸缩数据中获得的缓慢弛豫。我们证明了在磁输运中的弛豫与磁弛豫有着密切的关系，可以在有效介质近似的框架下理解，假设一阶参数与二阶参数成比例。
Emergent Spin-Filter at the interface between Ferromagnetic and Insulating Layered Oxides
我们报道了界面感应磁化对铁磁锰氧化物La $_{0.7}$ Ca $_{0.3}$ MnO $_{3}$和绝缘铜酸盐PrBa $_{2}$ Cu $_{3}$ O $_{7}$组成的磁性隧道结输运性质的强烈影响。与通常观察到的隧道磁阻随温度降低而稳定增加相反，该系统在低温下表现出突然的异常降低。有趣的是，这种异常行为可以归因于锰氧化物接触的正自旋极化和界面诱导的Cu磁化的负自旋过滤器效应之间的竞争。
Tailoring spin-orbit interactions and Coulomb repulsion are the key features to observe exotic physical phenomena such as magnetic anisotropy and topological spin texture at oxide interfaces. Our study proposes a novel platform for engineering the magnetism and spin-orbit coupling at LaMnO3/SrIrO3 (3d-5d oxide) interfaces by tuning the LaMnO3 growth conditions which controls the lattice displacement and spin-correlated interfacial coupling through charge transfer. We report on a tunable and enhanced interface-induced Rashba spin-orbit coupling and Elliot-Yafet spin relaxation mechanism in LaMn…
We investigate a series of manganese oxides, the La0.225Pr0.4(Ca1-xSrx)0.375MnO3 system. The x = 0 sample is a prototype compound for the study of phase separation in manganites, where ferromagnetic and charge ordered antiferromagnetic phases coexist. Replacing Ca2+ by Sr2+ gradually turns the system into a homogeneous ferromagnet. Our results show that the material structure plays a major role in the observed magnetic properties. On cooling, at temperatures below 100 K, a strong contraction of the lattice is followed by an increase in the magnetization. This is observed both through thermal e…
