We report a high-pressure study of orthorhombic rare-earth manganites AMnO3 using Raman scattering (for A = Pr, Nd, Sm, Eu, Tb and Dy) and synchrotron X-ray diffraction (for A = Pr, Sm, Eu, and Dy). In all cases, a structural and insulator-to-metal transition was evidenced, with a critical pressure that depends on the A-cation size. We analyze the compression mechanisms at work in the different manganites via the pressure dependence of the lattice parameters, the shear strain in the a-c plane, and the Raman bands associated with out-of-phase MnO6 rotations and in-plane O2 symmetric stretching modes. Our data show a crossover across the rare-earth series between two different kinds of behavior. For the smallest A-cations, the compression is nearly isotropic in the ac plane, with presumably only very slight changes of tilt angles and Jahn-Teller distortion. As the radius of the A-cation increases, the pressure-induced reduction of Jahn-Teller distortion becomes more pronounced and increasingly significant as a compression mechanism, while the pressure-induced bending of octahedra chains becomes conversely less pronounced. We finally discuss our results in the light of the notion of chemical pressure, and show that the analogy with hydrostatic pressure works quite well for manganites with small A-cations but can be misleading with large A-cations.
We use ab initio electronic structure calculations in combination with Monte Carlo simulations to investigate the magnetic and ferroelectric properties of bulk orthorhombic HoMnO$_3$ and ErMnO$_3$. Our goals are to explain the inconsistencies in the measured magnetic properties of the orthorhombic perovskite manganites (o-$R$MnO$_3$) with small rare-earth ($R$) cations or Y, as well as the contradictions between the directions and amplitudes of the electric polarizations reported by different experimental groups. Our computations stabilize several exotic magnetic orders (so-called w-spiral, H-…
We use resonant and non-resonant X-ray diffraction measurements in combination with first-principles electronic structure calculations and Monte Carlo simulations to study the relationship between crystal structure and multiferroic orders in the orthorhombic perovskite manganites, o-$R$MnO$_3$ ($R$ is a rare-earth cation or Y). In particular, we focus on how the internal lattice parameters (Mn-O bond lengths and Mn-O-Mn bond angles) evolve under chemical pressure and epitaxial strain, and the effect of these structural variations on the microscopic exchange interactions and long-range magnetic…
Long-Range Magnetic Interactions Induced by the Lattice Distortions and the Origin of the E-type Antiferromagnetic Phase in the Undoped Orthorhombic Manganites
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。
Bi(1-x)R(x)FeO(3)(R=rare earth): a family of novel magnetoelectrics
得到了Bi（1-x）R（x）FeO（3）固溶体的晶体，这里R= La，Dy，Gd，x ≤ 0.7。当x从0增加到0.7时，所述稀土的固溶体具有相同的五种晶体结构序列（菱形C3 v 6、三斜晶系C11、正交晶系D2 6、正交晶系D2 5、正交晶系C2 v 9）。在T=810-560°C时，铁电-顺电转变发生在菱面体和三斜晶系晶体中。正交结构C2 v 9保持高达1180°C。铁电畴结构在所有类型的晶体中是独特的。在具有D2（222）对称性的正交晶体中没有检测到磁电效应。而mm ~ 2晶体既有二次效应，又有线性效应，二次效应值比线性效应值小得多。在晶体中发生磁电磁滞现象。从晶体对称性的角度分析了所得晶体的张量性质。
Detailed investigations of structural, magnetic and electronic transport properties of hole-doped high-entropy rare-earth manganites are presented. The high-entropy samples (LaNdPrSmEu)$_{1-x}$Sr$_x$MnO$_3$ (0$\leq$\textit{x}$\leq$0.5), synthesized using the solid-state technique, show a change in the crystal structure from \textit{Pbnm} to \textit{R-3c} with increasing Sr substitution, attributed to the change in the tolerance factor. Prominent ferromagnetic ordering is observed in the sample with a rhombohedral structure (\textit{x}$\geq$0.3), originating from the dominant double exchange me…
Structural Domain Switching by Magnetic Fields in RAl$_3$C$_3$ (R=Rare Earth)
用X射线衍射研究了R = Yb，Tm，Er，Dy和Lu的RA1 $_3$ C $_3$的半方晶到正交晶的结构转变。我们报告如何通过调整外部磁场控制正交畴。结果表明，当R离子为磁性离子时，RA1 $_3$ C $_3$中的正交畴可以被磁场定向排列.它也表明，一个单畴状态可以切换到另一个单畴状态的字段，即使在顺磁状态与小的感应力矩。然而，对于R = Lu，不可能通过高达70 kOe的场来改变多畴状态。我们讨论了在RA1 $_3$ C $_3$的正交相中的磁各向异性引起的磁畴选择和开关。我们还提出了一个想法来解释Khalyavin等人[Phys. Rev. B \textbf{87}，220406（2013）]揭示的场诱导反铁磁性。
Spin reorientation and magnetisation reversal are two important features of the rare-earth orthorhombic provskites ($RM$O$_{3}$'s) that have attracted a lot of attention, though their exact microscopic origin has eluded researchers. Here, using density functional theory and classical atomistic spin dynamics we build a general Heisenberg magnetic model that allows to explore the whole phase diagram of the chromite and ferrite compounds and to scrutinize the microscopic mechanism responsible for spin reorientations and magnetisation reversals. We show that the occurrence of a magnetization rever…
Perovskite manganite La0.5Ca0.5-x xMnO3 (LCMO) nanomaterials were elaborated using the sucrose modified auto combustion method. Rietveld refinements of the X-ray diffraction patterns of the crystalline structure confirm a single-phase orthorhombic state with Pbnm space group (No. 62). The Ca-vacancies were voluntarily created in the LCMO structure in order to study their influence on the magnetic behaviour in the system. The magnetic susceptibility was found to be highly enhanced in the sample with Ca-vacancies. Paramagnetic-to-ferromagnetic phase transition was evidenced in both samples aroun…
In the multiferroic hexagonal manganite HoMnO3, inelastic neutron scattering and synchrotron based THz spectroscopy have been used to investigate the spin waves associated to the Mn order together with Ho crystal field excitations. While the Mn order sets in first below 80 K, a spin reorientation occurs below 37 K, a rare feature in the rare earth manganites. We show that severalHo crystal field excitations are present in the same energy range as the magnons, and that they are all affected by the spin reorientation. Moreover, several anomalous features are observed in the excitations at low te…
We have studied the structural stability of Sc-substituted rare earth (R) ferrites R1-xScxFeO3, and constructed a structural phase diagram for different R and x. While RFeO3 and ScFeO3 adopt the orthorhombic and the bixbyite structure respectively, the substituted compound R1-xScxFeO3 may be stable in a different structure. Specifically, for R0.5Sc0.5FeO3, the hexagonal structure can be stable for small R, such as Lu and Yb, while the garnet structure is stable for larger R, such as Er and Ho. The formation of garnet structure of the R0.5Sc0.5FeO3 compounds which requires that Sc occupies both…
The low-temperature spin dynamics of the orthorhombic TbFeO$_3$ perovskite has been studied. It has been found that the inelastic neutron scattering (INS) spectrum contains two modes corresponding to different sublattices in the compound. The iron subsystem orders antiferromagnetically at T$_N$ = 632 K and exhibits the high-energy magnon dispersion. Magnetic dynamics of this subsystem has been described using the linear spin wave theory and our solution yields sizable anisotropy between in-plane and out-of-plane exchange interactions. This approach was previously used to describe the magnon di…
