双层锰氧化物La $_{2-2x}$ Sr $_{1+2x}$ Mn $_2$ O $_7$（x=0.32）的磁畴调谐和磁泡畴的出现
Magnetic domain tuning and the emergence of bubble domains in the bilayer manganite La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ (x=0.32)
Juyoung Jeong, Ilkyu Yang, Jinho Yang, Oscar E. Ayala-Valenzuela, Dirk Wulferding, J. -S. Zhou, John B. Goodenough, Alex de Lozanne, John F. Mitchell, Neliza Le… 展开作者
Juyoung Jeong, Ilkyu Yang, Jinho Yang, Oscar E. Ayala-Valenzuela, Dirk Wulferding, J. -S. Zhou, John B. Goodenough, Alex de Lozanne, John F. Mitchell, Neliza Leon, Roman Movshovich, Yoon Hee Jeong, Han Woong Yeom, Jeehoon Kim
本文报道了层状锰氧化物La $_{2-2x}$ Sr $_{1+2x}$ Mn $_2$ O $_7$（含$x=0.32$）中磁畴演化的磁力显微镜研究。这种强相关电子化合物被认为具有广泛的磁相，包括最近发现的biskyrmion相。我们观察到一个连续的过渡，从树枝状条纹状域，随后形成的磁泡，由于场和温度依赖的竞争面内和面外的自旋对齐。磁泡相出现在可比的领域和温度范围的biskyrmion相，这表明两个阶段之间的密切关系。基于我们的真实空间图像，我们构建了这种组合物的温度场相图。
英文摘要：
We report a magnetic force microscopy study of the magnetic domain evolution in the layered manganite La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ (with $x=0.32$). This strongly correlated electron compound is known to exhibit a wide range of magnetic phases, including a recently uncovered biskyrmion phase. We observe a continuous transition from dendritic to stripe-like domains, followed by the formation of magnetic bubbles due to a field- and temperature dependent competition between in-plane and out-of-plane spin alignments. The magnetic bubble phase appears at comparable field- and temperature ranges as the biskyrmion phase, suggesting a close relation between both phases. Based on our real-space images we construct a temperature-field phase diagram for this composition.
Stretched exponential behavior in remanent lattice striction of a (La,Pr)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ bilayer manganite single crystal
本文研究了（La，Pr）$_{1.2}$ Sr $_{1.8}$ Mn $_{2}$ O $_{7}$单晶的弛豫磁致伸缩随时间的变化，以研究双层锰氧化物晶格畸变的慢动力学。双交换和Jahn-Teller型轨道-晶格相互作用之间的竞争导致所观察到的晶格轮廓遵循拉伸指数函数。这一发现表明，空间增长的本地晶格畸变加上电子$_{g}$ -电子轨道强烈相关的外观场诱导的CMR效应。
Spin freezing and magnetic inhomogeneities in bilayer manganites
我们对电子掺杂层状锰氧化物La $_{2-2x}$ Sr $_{1+2x}$ Mn $_2$ O $_7$（0.4< x<1）的多晶样品进行了μ子自旋旋转研究，以研究局域磁结构和自旋动力学。我们的研究结果提供了相分离为A型反铁磁相和电荷有序相的证据（x=0.52）和自旋冻结在低温（T<100K）（0.52<x<0.75）。提出了一个新的相图，其中包括这个自旋冻结区。
A high resolution, hard x-ray photoemission investigation of La_(2-2x)Sr_(1+2x)Mn_2O_7 (0.30<x<0.50): on microscopic phase separation and the surface electronic structure of a bilayered CMR manganite
Anisotropic phonon conduction and lattice distortions in CMR-type bilayer manganite (La$_{1-z}$Pr$_{z}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ (z=0,0.2,0.4 and 0.6) single crystals
本文系统地研究了（La $_{1-z}$ Pr $_{z}$）$_{1.2}$ Sr $_{1.8}$ Mn $_{2}$ O $_{7}$（$z$（Pr）= 0.2，0.4）单晶的热导率随温度和磁场的变化。和0.6。晶格畸变由于Pr-取代和各向异性的热导率在双层锰氧化物中的不同的弛豫模型的基础上提出的金属和绝缘状态的局部晶格畸变的Maderda等。巨磁热效应的缩放作为磁化强度的函数，并讨论了由于Pr-取代的$e_g$ -电子轨道状态的占领的系统变化的基础上。
The ground state of half-doped manganites involves intricate spin, charge and orbital orderings, which are difficult to discern experimentally. In this work, we resort to the theoretical analysis of the spin fluctuation spectrum of the half-doped bilayer Pr(Ca$_{0.9}$Sr$_{0.1}$)$_2$ Mn$_2$O$_7$ in order to get an insight of its electronic ground state. By means of the linear spin wave approximation, we compute the magnon dispersion for a family of localized spin models, which can describe several phases proposed for the ground state of half-doped manganites, like the intermediate one proposed …
Based on the two-variable polynomial model of magnetization, magnetic entropy change of bilayered manganites with $327$-structure and its scaling behaviour with respect to applied magnetic fields are investigated. It's found that the Curie temperature, which is defined as the point at which the partial derivative of magnetization with respect to temperature reaches its maximum, is different from the temperature of peak magnetic entropy change. Thus a mean-field model can not apply to this kind of manganites. In contrast to what has been found in manganites with the $113$-structure, the scaling…
Investigation of ferromagnetic domain behavior and phase transition at nanoscale in bilayer manganites
理解锰氧化物中巨磁电阻的基本机制和现象学主要集中在原子和纳米级物理学上，如双交换，相分离和电荷顺序。在这里，我们认为一个更宏观的观点的锰氧化物材料的物理，报告的铁磁畴行为在一个双层锰氧化物样品的名义组成的La $_{2-2x}$ Sr $_{1+2x}$ Mn $_2$ O $_7$与$x=0.38$，研究使用原位洛伦兹透射电子显微镜。阐明了磁晶各向异性对畴壁结构的作用。在冷却时，在$a-b$平面内的居里温度下，可以看到磁畴对比度首先出现。随着温度的进一步降低，磁畴面积分数的变化被用来估计描述铁磁相变的临界指数。铁磁相变伴随着一个独特的纳米级颗粒对比接近居里温度，我们推断这是与铁磁纳米团簇的存在下，在一个顺磁性的矩阵，这还没有在双层锰氧化物的报道。
Steplike Lattice Deformation of Single Crystalline (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ Bilayered Manganite
本文报道了（La $_{0.4}$ Pr $_{0.6}$）$_{1.2}$ Sr $_{1.8}$ Mn $_{2}$ O $_{7}$双层锰氧化物的阶梯状晶格转变，并伴随着磁化和磁阻跃变，研究了场致一级相变的超尖锐性质，即从顺磁性绝缘体到铁磁性金属相的转变，并伴随着电阻的巨大下降.我们的研究结果支持，突然的磁致伸缩是密切相关的轨道挫折存在于不均匀的顺磁绝缘相，而不是竞争的两相之间的马氏体的情况。
Magnetic and orbital order in overdoped bilayer manganites
在掺杂区$0.5 < x <1.0$的双层锰氧化物的磁性和轨道的顺序已经从一个模型，该模型包括两个$e_g$轨道在每个Mn站点，轨道间的库仑相互作用和晶格畸变进行了研究。通常的双交换通过$e_g$轨道进行。它示出，这样的模型再现最近获得的双层系统在此范围内的掺杂的相图。由Ling等人看到的具有（$π,0,π$）自旋序的C型相似乎是分层几何结构的自然结果，并且通过系统的静态畸变而稳定。的轨道顺序示出驱动磁顺序，而各向异性跳跃的$e_g$轨道，分层的基本结构和相关的静态失真的性质在很大程度上决定了轨道安排。
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。
Magneto-optical investigation of the field-induced spin-glass insulator to ferromagnetic metallic transition of the bilayer manganite (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$
为了研究磁场驱动自旋玻璃绝缘体到铁磁金属的转变，我们测量了（$_{0.4}$ Pr $_{0.6}$）$_{1.2}$ Sr $_{1.8}$ Mn $_2$ O $_7$的磁光响应.磁场的应用恢复铁磁状态的电子结构的整体红移，增长的束缚载流子本地化与铁磁域，发展的赝能隙，软化的Mn-O的伸缩和弯曲模式，表明结构的变化。我们讨论了领域和温度引起的趋势的框架内的富冈Tokura全球电子相图图片，并建议控制无序附近的相边界可以用来调整磁介电响应。自旋玻璃绝缘体到铁磁金属转变的恢复也可以驱动（La $_{0.4}$ Pr $_{0.6}$）$_{1.2}$ Sr $_{1.8}$ Mn $_2$ O $_7$中的300 K颜色变化。
Transmission of information using the spin of the electron as well as its charge requires a high degree of spin polarization at surfaces. At surfaces however this degree of polarization can be quenched by competing interactions. Using a combination of surface sensitive x-ray and tunneling probes, we show for the quasi-two-dimensional bilayer manganites that the outermost Mn-O bilayer, alone, is affected: it is a 1-nm thick insulator that exhibits no long-range ferromagnetic order while the next bilayer displays the full spin polarization of the bulk. Such an abrupt localization of the surface …
Antiferromagnetic Domain Structure in Bilayer Manganite
本文报道了一种新的软X射线纳米衍射研究强关联层状锰氧化物La $_{0.96}$ Sr $_{2.04}$ Mn $_{2}$ O $_{7}$中的反铁磁畴。我们发现，反铁磁畴淬火，形成一个独特的域模式，每个域具有其自旋方向的固有记忆，并与相关的畴壁沿结晶方向运行。这可以通过在晶体生长过程中锁定的晶体或磁性缺陷的存在来解释，这些缺陷钉扎反铁磁畴。反铁磁畴图案显示两种不同类型的域。我们观察到，在一种类型中，在锰自旋方向上的周期性波纹，周期约为4 \micro \meter。我们建议，双层内的反转对称性的损失是负责通过Dzyaloshinskiii-Moriya型相互作用的这种波纹结构。
Evidence for nano-scale inhomogeneities in bilayer manganites in the Mn\sp{4+} rich region: $\bm{0.54 \leq x \leq 0.80}$
采用原子对分布函数（PDF）技术研究了掺杂范围为$0.54 \leq x \leq 0.80$的天然双层锰氧化物\lsmo中原子的局域结构响应。我们的低温中子粉末衍射测量表明，当其有序磁结构从A型（$0.54 \leq x \leq 0.66$）向C/C型$^*$（$0.74 \leq x \leq 0.90$）有序过渡时，两种不同的Jahn-Teller（JT）畸变MnO $_6$八面体共存。在低温下，在所有掺杂水平下，掺杂空穴主要存在于双层的平面中。在A型磁有序区中，$_g$电子在平面上明显离域，形成未畸变的八面体，而在C/C型$^*$区中，JT畸变八面体明显拉长.这与非均匀共存的离域和局域电子态的存在是一致的。没有观察到宏观相分离的证据。这种纳米级的不均匀性可以解释在自旋无序的“间隙”区域（$0.66 \leq x \leq 0.74$）中观察到的磁阻挫行为。
Colossal electroresistance and colossal magnetoresistive step in paramagnetic insulating phase of single crystalline bilayered manganite(La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$
我们报告了在（La $_{0.4}$ Pr $_{0.6}$）$_{1.2}$ Sr $_{1.8}$ Mn $_{2}$ O $_{7}$的顺磁绝缘（PMI）状态下在$ab$ -平面上施加电流引起的低温电阻的显著降低。在较低的温度下观察到一个巨大的电阻效应，达到~ 95%。在低于10 K的低温下，在5 T附近出现一个巨大的磁阻阶跃，并伴随着绝缘体-金属转变的超尖锐宽度。向晶体注入更高的电流会导致阶跃跃迁消失。这些发现与研究晶体的PMI矩阵内钉扎的短程电荷有序簇的存在有密切的关系。
我们研究了电子掺杂锰氧化物所表现出的各向异性磁结构，使用一个模型，该模型结合了轨道简并的$e_{g}$电子之间的双交换和$t_{2g}$电子之间的超交换与Hund的耦合（$J_H$），超交换耦合（$J_{AF}$）和带宽（$W$）的实际值。我们研究了G型、C型和A型反铁磁相的相对稳定性。特别是，我们发现，G相是稳定的低电子掺杂，如在实验中看到的。我们发现与实验观察到的电子掺杂锰氧化物（$x > 0.5$），如Nd $_{1-x}$ Sr $_{x}$ MnO $_{3}$，Pr $_{1-x}$ Sr $_{x}$ MnO $_{3}$和Sm $_{1-x}$ Ca $_{x}$ MnO $_{3}$的磁相图很好的协议。我们还可以解释实验观察到的C和A相的轨道结构。我们还扩展了我们的电子掺杂双层锰氧化物的形式R $_{2-2x}$ A $_{1+2x}$ Mn $_2$ O $_7$的计算，并预测，C-相将在这些系统中，由于其减少的维数缺席。
Large magnetocapacitance in electronic ferroelectric manganite systems
我们已经观察到一个相当大的正磁电容钙钛矿中的（$\sim$ $5-90\%$）Pr $_{0.55}$ Ca $_{0.45}$ Mn O $_3$和双层Pr（Sr $_{0.1}$ Ca $_{0.9}$）$_2$ Mn $_2$ O $_7$系统在5 T磁场下跨越20- 10 0 K以下的磁性转变点T $_N$。另一方面，磁介电效应表现出交叉：（a）在相同的温度范围内，钙钛矿系统从正到负，以及（b）双层系统从负到正。双层Pr（Sr $_{0.1}$ Ca $_{0.9}$）$_2$ Mn $_2$ O $_7$体系也表现出相当大的各向异性。我们还注意到磁场对这些体系介电弛豫特性的影响。这些系统属于一类不适当的铁电体，并预计表现出电荷/轨道顺序驱动的铁电极化低于转变点T $_{CO}$。在这些系统中的大的磁电容表现出典型的多铁性行为，即使铁电极化是小的相比，其他铁电体。
Orientation-driven route to an intrinsic insulating ferromagnetic state in manganite superlattices
Uppsala University（乌普萨拉大学）；Asia Pacific Center for Theoretical Physics（亚太理论物理中心）；King Abdullah University of Science and Technology (KAUST)（阿卜杜拉国王科技大学）；Institute of Physics, Nicolaus Copernicus University（尼古拉·哥白尼大学物理研究所）；School of Physics, Engineering and Technology, University of York（约克大学物理、工程与技术学院）；Department of Physics and Institute of Quantum Convergence and Technology, Kangwon National University（江原国立大学物理系及量子融合技术研究所）；University of Aberdeen（阿伯丁大学）
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…
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