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。
英文摘要:
We report a novel soft x-ray nanodiffraction study of antiferromagnetic domains in the strongly correlated bylayer manganite La$_{0.96}$Sr$_{2.04}$Mn$_{2}$O$_{7}$. We find that the antiferromagnetic domains are quenched, forming a unique domain pattern with each domain having an intrinsic memory of its spin direction, and with associated domain walls running along crystallographic directions. This can be explained by the presence of crystallographic or magnetic imperfections locked in during the crystal growth process which pin the antiferromagnetic domains. The antiferromagnetic domain pattern shows two distinct types of domain. We observe, in one type only, a periodic ripple in the manganese spin direction with a period of approximately 4 \micro\meter. We propose that the loss of inversion symmetry within a bilayer is responsible for this ripple structure through a Dzyaloshinskii-Moriya-type interaction.
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…
Delta Doping of Ferromagnetism in Antiferromagnetic Manganite Superlattices
我们证明,三角洲掺杂可以用来创建一个尺寸限制区域的金属铁磁性的反铁磁(AF)锰氧化物主机,而不会引入任何明确的混乱,由于掺杂剂或挫折的自旋。用数字合成技术将δ掺杂载流子插入到锰氧化物超晶格中。这些额外的载流子的理论考虑表明,它们导致局部增强铁磁(F)双交换相对于AF超交换,导致局部倾斜的AF自旋。这导致了高度调制的磁化,如通过极化中子反射计测量的。倾斜的空间调制与电荷从掺杂层的扩散有关,并且建立了这些锰氧化物中的电荷转移、轨道占据和磁序的变换的基本长度尺度。此外,我们证实了存在的倾斜,AF状态的预测由德Gennes [P.- G. de Gennes,Phys. Rev. 118,141(1960)],但仍然难以捉摸。
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。
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 …
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。
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。
Orbital mixing and nesting in the bilayer manganites La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$
La $_{2-2x}$ Sr $_{1+2x}$ Mn $_2$ O $_7$化合物的掺杂水平$0.3\leq x\leq 0.5$的第一原理研究表明,低能量的多数自旋载流子的电子结构是由强大的动量依赖的Mn $e_g$ $d_{x^2-y^2}$和$d_{3z^2-r^2}$轨道之间的相互作用,除了$x$依赖的Jahn-Teller失真,不同的铁磁和反铁磁相。费米表面表现出嵌套行为,反映了在静态磁化率,其位置作为动量的函数有一个非平凡的依赖$x$的峰值。
Here, we propose quantum spin Hall-like phononic states in van der Waals bilayer systems with antiferromagnetic ordering. Antiferromagnetic ordering in bilayer systems with small interlayer interaction makes the total Chern number zero, where the Chern numbers for each layer are opposite to each other. In bilayer CrI3 where antiferromagnetic ordering has been experimentally demonstrated, we show that the quantum spin Hall-like states appear with spatially separated chiral edge modes.
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。
Long-Range Magnetic Interactions Induced by the Lattice Distortions and the Origin of the E-type Antiferromagnetic Phase in the Undoped Orthorhombic Manganites
We report the current-driven dynamics of frustrated skyrmions in an antiferromagnetically exchange coupled bilayer system, where the bilayer skyrmion consists of two monolayer skyrmions with opposite skyrmion numbers $Q$. We show that the in-plane current-driven bilayer skyrmion moves in a straight path, while the out-of-plane current-driven bilayer skyrmion moves in a circular path. It is found that the in-plane current-driven mobility of a bilayer skyrmion is much better than the monolayer one at a large ratio of $β/α$, where $α$ and $β$ denote the damping parameter and non-adiabatic spin tr…
The interlayer magnetic interaction in bilayer CrI$_3$ plays a crucial role for its device applications. In this work, we studied the interlayer magnetic interaction in $π/3$-twisted bilayer CrI$_3$ using first-principles calculations. Our calculations show that the interlayer coupling can be ferromagnetic or antiferromagnetic depending crucially on lateral shift. The strongest antiferromagnetic interlayer interaction appears in the $\bar{A}A$-stacking. The magnetic force theory calculations demonstrate that such an antiferromagnetic interaction is dominanted by the $e_g$-$e_g$ channel. Partic…
Twisting in bilayers introduces structural chirality with two enantiomers, i.e., left- and right-hand bilayers, depending on the oriented twist angle. The interplay between this global chirality and additional degrees of freedom, such as magnetic ordering and the local octahedral chirality arising from the geometry of the bonds, can yield striking phenomena. In this work, we focus on collinear antiferromagnetic CrI$_3$ twisted homo-bilayers, which are characterized by a staggered octahedral chirality in each monolayer. Using symmetry analysis, density functional theory and tight-binding model …
The Structural and Magnetic ordering in $La{}_{0.5-x}Nd_{x}Ca_{0.5}MnO_{3}$ (0.1 \ensuremath{\le} x \ensuremath{\le} 0.5) Manganites
用磁化强度、电阻率、透射电子显微镜和中子衍射技术研究了多晶$La{}_{0.5-x}Nd{}_{x}Ca_{0.5}MnO{}_{3}$(0.0 \ensuremath{\le} x \ensuremath{\le} 0.5)样品的晶体和磁性结构。样品具有正交结构,空间群为\textit{Pnma}。随着温度的降低,样品呈现出CE型反铁磁结构,同时存在弱的铁磁有序.铁磁相的生长削弱了电荷和轨道有序的反铁磁相。低温下Nd掺杂引起的结构畸变和磁结构的演化与A位无序($σ^{2}$)有很强的相关性。
The spin Hall magnetoresistance (SMR) and anomalous Hall effect (AHE) are observed in a Cr2O3/Ta structure. The structural and surface morphology of Cr2O3/Ta bilayers have been investigated. Temperature dependence of longitudinal and transverse resistances measurements confirm the relationship between SMR and AHE signals in Cr2O3/Ta structure. By means of temperature dependent magnetoresistance measurements, the physical origin of SMR in the Cr2O3/Ta structure is revealed, and the contribution to the SMR from the spin current generated by AHE has been proved. The so-called boundary magnetizati…
Galvanomagnetic effects and manipulation of antiferromagnetic interfacial uncompensated magnetic moment in exchange-biased bilayers
本文研究了IrMn $_{3}$ /绝缘-Y $_{3}$ Fe $_{5}$ O $_{12}$交换偏置双层膜。反铁磁体中的净磁矩$Δm_{AFM}$的行为直接由反常和平面霍尔效应和各向异性磁阻探测。证明了$Δm_{AFM}$来自于界面未补偿的磁矩。我们证明了交换偏置和转动滞后是由$Δm_{AFM}$的不可逆开关引起的。在训练效果中,$Δm_{AFM}$持续变化。这项工作突出了$Δm_{AFM}$在交换偏置中的基本作用,有利于反铁磁自旋电子器件的操纵。
Robust and tunable Floquet altermagnets in sliding A-type antiferromagnetic bilayers
Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences(中国科学院物理研究所,凝聚态物理北京国家实验室);Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (Ministry of Education), School of Physics, Beijing Institute of Technology(北京理工大学物理学院,先进光电子量子架构与测量教育部重点实验室,量子物理中心);University of Chinese Academy of Sciences(中国科学院大学);Songshan Lake Materials Laboratory(松山湖材料实验室)