在最佳掺杂的锰氧化物（ODM）中，伴随着极化子的形成的复杂玻璃化现象的物理基础是一个棘手的问题，有许多无法解释的方面。本文报道了ODM La $_{0.67}$ Ca $_{0.33}$ MnO $_3$在80 K-900 K温度范围内的$^{139}$ La和$^{55}$ Mn NMR谱。我们发现，局部晶格畸变，建立在顺磁（PM）相$T<700$ K，诱导一个真正的自旋玻璃态，这对于$T<T_c$巩固与铁磁（FM）状态成一个单一的热力学相。La $_{0.77}$ Ca $_{0.23}$ MnO $_3$的比较NMR实验，La $_{0.59}$ Ca $_{0.41}$ MnO $_3$，和La $_{0.70}$ Sr $_{0.30}$ MnO $_3$证明了晶格畸变的主导作用，其似乎控制（i）自旋玻璃相组分的稳定性和（ii）PM-FM相变的种类（第一或第二阶）。实验结果与可压缩随机键-随机场伊辛模型的预测一致，其中考虑晶格畸变引起的应变场，显示在$T_c$调用FM和“玻璃态”爱德华-安德森（EA）序参数的不连续（1阶样）变化。
英文摘要：
The physics underlying the complex glassy phenomena, which accompany the formation of polarons in optimally doped manganites (ODM) is a cumbersome issue with many unexplained aspects. In this article we present $^{139}$La and $^{55}$Mn NMR in the temperature range 80K - 900K of ODM La$_{0.67}$Ca$_{0.33}$MnO$_3$. We show that local lattice distortions, established in the Paramagnetic (PM) phase for $T<700$K, induce a genuine spin-glass state, which for $T<T_c$ consolidates with the Ferromagnetic (FM) state into a single thermodynamic phase. Comparative NMR experiments on La$_{0.77}$Ca$_{0.23}$MnO$_3$, La$_{0.59}$Ca$_{0.41}$MnO$_3$, and La$_{0.70}$Sr$_{0.30}$MnO$_3$ demonstrate the dominant role of lattice distortions, which appear to control (i) the stability of the spin glass phase component and (ii) the kind (1st or 2nd order) of the PM-FM phase transition. The experimental results are in agreement with the predictions of the compressible random bond - random field Ising model, where consideration of a strain field induced by lattice distortions, is shown to invoke at $T_c$ a discontinuous (1st order like) change of both the FM and the "glassy" Edwards-Anderson (EA) order parameters.
Phase separation and the possibility of orbital liquid states in CMR manganites. A 139La NMR study
139 La NMR自旋-晶格弛豫速率1/T1和射频增强实验提供的证据表明，低温制度的铁磁（FM）相的La 1-xCaxMnO 3隔离成高导电性和导电性差的FM区域，与轨道结构的差异。值得注意的是，相分离伴随着一个额外的NMR信号的外观从FM区域与消失的小磁各向异性。这一特征被归因于具有强烈轨道波动的区域的出现，类似于不均匀FM矩阵内的轨道液体的液滴。
Spin Dynamics of Double-Exchange Manganites with Magnetic Frustration
本文研究了双交换模型中由于竞争的铁磁和反铁磁海森堡相互作用引起的磁阻挫对自旋动力学的影响。当局域矩不共线时，电荷密度波形成，因为电子更喜欢坐在铁磁耦合的位置线上。随着跳跃能量的增加，局域自旋变得对齐，平均自旋波刚度增加。相分离被发现只在一个狭窄的范围内的跳跃能量。这项工作的结果被施加到观察到的锰氧化物Pr $_{1-x}$ Ca $_x$ MnO $_3$与$0.3 \le x \le 0.4$的自旋波刚度的场致跳跃。
Phase Separation in A-site Ordered Perovskite Manganite LaBaMn$_2$O$_6$ Probed by $^{139}$La and $^{55}$Mn NMR
$^{139}$ La-和$^{55}$ Mn-NMR谱表明，A位有序钙钛矿锰氧化物LaBaMn $_2$ O $_6$的基态是铁磁（FM）和反铁磁（AFI（CE））区域的空间混合物，这分别被分配给金属和绝缘电荷有序状态。这种奇异的共存状态出现在200 K以下，通过一个一阶类似的形成的AFI（CE）状态内的FM之一。Mn自旋-自旋弛豫速率表明，$_2$中与AFI（CE）区共存的FM区与无序形式La $_{0.5}$ Ba $_{0.5}$ MnOPDMATHABMR的体FM相相同，尽管没有A位无序.这表明LaBaMn $_2$ O $_6$中FM区的介观性质而不是纳米性质。
Antiferromagnetic Order and Magnetic Frustration in the Honeycomb Heavy-Fermion System Ce(Pt$_{1-x}$Pd$_{x}$)$_6$Al$_3$: $^{27}$Al and $^{195}$Pt NMR Studies
Site-specific $^{13}$C NMR study on locally distorted triangular lattice of organic conductor $κ$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$
为了验证几何挫折的影响，我们人为扭曲的三角形晶格准二维有机导体$κ$ -（BEDT-TTF）$_2$铜$_2$（CN）$_3$ [BEDT-TTF：双（亚乙基二硫代）四硫富瓦烯]通过类似的分子取代和应用$^{13}$ C NMR的散装和取代的网站，电导率，静态磁化率测量。结果表明，取代样品的磁特性与纯样品的磁特性在数量上相似。此外，在替代位置处的磁特性也与体中相同。这些结果表明，所观察到的磁性可能不是由于几何挫折，但无序的重要性。
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。
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。
We report on a detailed neutron diffraction and $^1$H-NMR study on the frustrated spin-1/2 chain material linarite, PbCuSO$_4$(OH)$_2$, where competing ferromagnetic nearest neighbor and antiferromagnetic next-nearest neighbor interactions lead to frustration. From the magnetic Bragg peak intensity studied down to 60 mK, the magnetic moment per Cu atom is obtained within the whole magnetic phase diagram for $H \parallel b$ axis. Further, we establish the detailed configurations of the shift of the SDW propagation vector in phase V with field and temperature. Finally, combining our neutron diff…
$^{31}$P nuclear magnetic resonance (NMR) measurements have been carried out to investigate the magnetic properties and spin dynamics of Fe$^{3+}$ ($S$ = 5/2) spins in the two-dimensional triangular lattice (TL) compound Na$_3$Fe(PO$_4$)$_2$. The temperature ($T$) dependence of nuclear spin-lattice relaxation rates ($1/T_1$) shows a clear peak around Néel temperature, $T_{\rm N} = 10.9$~K, corresponding to an antiferromagnetic (AFM) transition. From the temparature dependence of NMR shift ($K$) above $T_{\rm N}$, an exchange coupling between Fe$^{3+}$ spins was estimated to be $J/k_{\rm B}\sim…
NMR evidence of pressure-induced structural transition and enhanced spin fluctuations up to 14~GPa in SrCu$_2$(BO$_3$)$_2$
School of Physics and Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education), Renmin University of China（中国人民大学物理学院和量子态构建与操控教育部重点实验室）；Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics（中国科学院物理研究所和北京凝聚态物理国家实验室）
We report x-ray diffraction, magnetic susceptibility, heat capacity, $^{1}$H nuclear magnetic resonance (NMR), and muon spin relaxation ($μ$SR) measurements, as well as density-functional band-structure calculations for the frustrated $S=3/2$ triangular lattice Heisenberg antiferromagnet (TLHAF) $α$-HCrO$_{2}$ (trigonal, space group: $R\bar{3}m$). This compound undergoes a clear magnetic transition at $T_{\rm N} \simeq 22.5$~K, as seen from the drop in the muon paramagnetic fraction and concurrent anomalies in the magnetic susceptibility and specific heat. Local probes (NMR and $μ$SR) reveal a…
We report on the results of 23Na NMR in the honeycomb lattice magnet Na2Co2TeO6 which has been nominated as a Kitaev material. Measurements of magnetic shift and width of the NMR line as functions of temperature and magnetic field show that a spin-disordered phase does not appear up to a field of 9 T. In the antiferromagnetic phase just below the Neel temperature TN, we find a temperature region extending down to ~TN/2 where the nuclear spin-lattice relaxation rate 1/T1 remains enhanced and is further increased by a magnetic field. This region crosses over to a low temperature region character…
Mutual interactions in many-body systems bring about a variety of exotic phases, among which liquid-like states failing to order due to frustration are of keen interest. Recently, an organic system with an anisotropic triangular lattice of molecular dimers has been suggested to host a dipole liquid arising from intradimer charge-imbalance instability, possibly offering an unprecedented stage for the spin degrees of freedom. Here we show that an extraordinary unordered(unfrozen) spin state having soft-matter-like spatiotemporal characteristics is substantiated in this system. $^1$H NMR spectra …
We report a $^{35}$Cl nuclear magnetic resonance (NMR) study of the diluted Kitaev material $α$-Ru$_{1-x}$Ir$_x$Cl$_3$ ($x=0.1$ and $0.2$) where non-magnetic Ir$^{3+}$ dopants substitute Ru$^{3+}$ ions. Upon dilution, the $^{35}$Cl spectra exhibit unusual large magnetic inhomogeneity, which sets in at temperatures below the Kitaev exchange energy scale. At the same time, the $^{35}$Cl spin-lattice relaxation rate $T_1^{-1}$ as a function of dilution and magnetic field unravels a critical doping of $x_c\approx 0.22$, towards which both the field-induced spin gap and the zero-field magnetic orde…
We report the structural and magnetic properties of a new system LiRhMnO$_{4}$ (LRMO) through x-ray diffraction, bulk magnetization, heat capacity and $^{7}$Li nuclear magnetic resonance (NMR) measurements. LRMO crystallizes in the cubic space group $\mathit{Fd}$$\bar{3}$$\mathit{m}$. From the DC susceptibility data, we obtained the Curie-Weiss temperature $\mathrmθ_{\mathrm{CW}}$ = -26 K and Curie constant $\mathit{C}$ = 1.79 Kcm$^{3}$/mol suggesting antiferromagnetic correlations among the magnetic Mn$^{4+}$ ions with an effective spin $\mathit{S}$ = $\frac{3}{2}$. At $\mathit{H}$ = 50 Oe, t…
Theory of the field-induced BEC in the frustrated spin-1/2 dimer compound BaCuSi2O6
最近的中子和NMR实验的基础上，我们调查的领域引起的外来临界观察到的挫折自旋1/2二聚体化合物BaCuSi 2 O 6使用挫折模型与两种类型的双层。有效的硬核玻色子模型的半经典处理表明，完美的层间挫折导致一个2D的临界指数φ =1，没有对数校正和3D低温相不同，但非零三重态人口在两种类型的双层。这些结果进一步表明，一个简单的现象，在一个依赖于场的横向耦合的上下文中，我们重现整个场-温度相图与量子蒙特卡罗模拟。
We report on the low-energy dynamics in the kagome antiferromagnet CaCu$_3$(OD)$_6$Cl$_2\cdot0.6$D$_2$O (Ca-kapellasite) as studied by use of $^2$D-NMR measurements. Previous $^{35}$Cl-NMR measurements revealed that the nuclear spin-lattice relaxation rate ($1/T_1$) shows two peaks at temperatures, $T^{\ast} = 7.2$ K and $T_s \simeq 25$ K. While the low-temperature peak at $T^{\ast}$ is ascribed to the critical fluctuations near the long-range magnetic ordering, the origin of the high-temperature peak has not been fully understood. From the $1/T_1$ measurements on the D sites at the OD groups …
