High activity is one of the primary requirements for the catalysts in proton exchange membrane fuel cell applications. Platinum (Pt) is the best known catalyst, especially for oxygen reduction at the cathode; however, further activity improvements are still required. Previous computational studies suggested that the catalytic activity of Pt nanoparticles could be enhanced by a $\mathrm{Pt}\text{−}\mathrm{carbon}$ (C) support interaction. We have recently found that an enhanced electronic interaction occurs at the interface between an argon-ion (${\mathrm{Ar}}^{+}$)-irradiated glassy carbon (GC) surface and Pt nanoparticles. Here, we report a more than twofold increase in specific activity for the Pt nanoparticles on the ${\mathrm{Ar}}^{+}$-irradiated GC substrate compared to that on the nonirradiated GC substrate. The mechanism of this activity enhancement was investigated by local structure analysis of the interface. ${\mathrm{Ar}}^{+}$ irradiation of the carbon support led to the formation of $\mathrm{Pt}\text{−}\mathrm{C}$ bonding, thus protecting the deposited Pt nanoparticles from oxidation.

We combine ab initio simulations and Raman scattering measurements to demonstrate explicit anharmonic effects in the temperature-dependent dielectric response of a NaCl single crystal. We measure the temperature evolution of its Raman spectrum and compare it to both a quasiharmonic and anharmonic model. Results demonstrate the necessity of including anharmonic lattice dynamics to explain the dielectric response of NaCl, as it is manifested in Raman scattering. Our model fully captures the linear dielectric response of a crystal at finite temperatures and may therefore be used to calculate the temperature dependence of other material properties governed by it.

Molecular-beam epitaxy (MBE) is the gold standard for the epitaxial growth of complex oxides with the best material properties as determined by respective figures of merit. Unfortunately, once more than one cation is involved in the material desired, MBE growth often becomes plagued by difficulties in stoichiometry control. Instead of relying on a quartz crystal microbalance to measure the fluxes of the individual molecular beams, which lacks accuracy, or reflection high-energy electron diffraction oscillations of the targeted multication oxide in layer-by-layer growth, which lacks general applicability, here, we describe a canonical approach based on the growth of films of the constituent binary oxides or metals individually for cation flux calibration. This method can calibrate the flux of each molecular beam with an absolute accuracy of ±1%. After describing the growth parameters of binary oxides or metals enabling the individual fluxes of 39 elements of the periodic table to be determined, we demonstrate the efficacy of this approach by applying it to the growth of the quaternary ferromagnetic metal ${\mathrm{La}}_{0.5}{\mathrm{Sr}}_{0.5}\mathrm{Co}{\mathrm{O}}_{3-\delta }$ to achieve films with transport properties rivalling the best reported using thin-film growth techniques providing stoichiometric transfer.

Constructing two-dimensional (2D) van der Waals (vdW) heterostructures is a promising strategy to improve the photocatalytic efficiency of a single 2D material and has attracted wide attention. Here, the electronic structures, optical properties, and photocatalytic mechanism of the 2D GeC/BSe vdW heterostructure are investigated by first-principles calculations. It is demonstrated that the GeC/BSe heterostructure is comparatively very stable and possesses a staggered band alignment configuration. An intrinsic built-in electric field from the GeC layer to the BSe layer would be established at the interface, allowing the formation of Z-scheme charge transfer mode in the GeC/BSe heterostructure. Furthermore, its band edges exactly straddle the water redox potentials; overall water splitting can thus be expected. The GeC/BSe heterostructure also has a good light absorption coefficient with the magnitude order of ${10}^5\mathrm{c}{\mathrm{m}}^{-1}$. Moreover, it is proposed that the adoption of tensile strain can further promote the optical absorptions in the visible light range because of the favorable modulation in the bandgap, which benefits the photocatalytic reaction. Finally, the excellent abilities of ${\mathrm{H}}_2\mathrm{O}$ adsorption and ${\mathrm{H}}_2$ desorption are shown in the GeC/BSe heterostructure. These features make the GeC/BSe heterostructure promising for application in photocatalysis for water splitting.

We report a systematic study on the structural and magnetic properties of off-stoichiometric polycrystalline bulk spinels ${\mathrm{Mn}}_{1.15}{\mathrm{Co}}_{1.85}{\mathrm{O}}_4$ and ${\mathrm{Mn}}_{1.17}{\mathrm{Co}}_{1.60}{\mathrm{Cu}}_{0.23}{\mathrm{O}}_4$ using neutron and x-ray diffraction, ferromagnetic resonance, and magnetic measurements. Both compounds show a weak tetragonal distortion with $c/a<1$, where the crystal structure could be refined in the tetragonal space group $I{4}_1/amd$. Both ${\mathrm{Co}}^{2+}$ and ${\mathrm{Cu}}^{2+}$ ions are located at the tetrahedral $A$ site, and ${\mathrm{Mn}}^{3+}$ and ${\mathrm{Co}}^{3+}$ at the octahedral $B$ site. Ferrimagnetic (FI) ordering of ${\mathrm{Mn}}_{1.15}{\mathrm{Co}}_{1.85}{\mathrm{O}}_4$ and ${\mathrm{Mn}}_{1.17}{\mathrm{Co}}_{1.60}{\mathrm{Cu}}_{0.23}{\mathrm{O}}_4$ sets in below 184 and 164 K, respectively. Magnetic structure analysis revealed that the ferrimagnetically coupled $A^{2+}$- and $B^{3+}$-site moments are aligned parallel to the tetragonal $c$ axis. Additionally, a noncollinear antiferromagnetic order appears in the $ab$ plane, where the moments point along [110] and $\left[1\overline{1}0\right]$. The net magnetic moment [$2{\mu }_{\mathrm{FI}}({\mathrm{Mn}}_B$/${\mathrm{Co}}_B)-{\mu }_{\mathrm{FI}}({\mathrm{Co}}_A$)] of ${\mathrm{Mn}}_{1.15}{\mathrm{Co}}_{1.85}{\mathrm{O}}_4$ obtained from neutron data varies between 0.88–1.08 ${\mu }_B$ which is in good agreement with $M=0.89\text{–}1.13$ ${\mu }_B$ as determined from magnetization measurements. However, for the Cu-containing compound a larger discrepancy in the magnetic moment was observed between the neutron data (1.89–1.92 ${\mu }_B$) and low-temperature ($T=1.9$ K) field-dependent ($H=90$ kOe) magnetization data ($0.97\text{–}1.21$ ${\mu }_B$). From the three-sublattice model we obtained canting angles ${28}^{\circ }$ and ${25}^{\circ }$ for ${\mathrm{Mn}}_{1.15}{\mathrm{Co}}_{1.85}{\mathrm{O}}_4$ and ${\mathrm{Mn}}_{1.17}{\mathrm{Co}}_{1.60}{\mathrm{Cu}}_{0.23}{\mathrm{O}}_4$, respectively. Both the bulk systems exhibit high magnetocrystalline anisotropy ($K_{\text{U}}\sim 9\times {10}^5$ and $7.5\times {10}^5$ erg/${\mathrm{cm}}^3$) and a field-induced transition ($H_{\text{D}}$) across 4.0 kOe due to the domain reorientation. Temperature ($1.9\text{–}350$ K) and field ($\pm 90$ kOe) dependence of magnetization data confirms the high-spin ($S=\frac{3}{2}$ and $S=2$) ground-state configuration for both the divalent Co and trivalent Mn.

We consider theoretically the paramagnetic phases of $\mathrm{EuTi}{\mathrm{O}}_3$ that represent configurations created by two sets of microscopic degrees of freedom (m-DOFs): positional symmetry breaking due to octahedral rotations and magnetic symmetry breaking due to spin disorder. The effect of these sets of m-DOFs on the electronic structure and properties of the para phases is assessed by considering sufficiently large (super) cells with the required nominal global average symmetry, allowing, however, the $local$ positional and magnetic symmetries to be lowered. We find that tendencies for local symmetry breaking can be monitored by following total energy lowering in mean-fieldlike density-functional theory, without recourse for strong correlation effects. While most nominally cubic $AB{\mathrm{O}}_3$ perovskites are known for their symmetry breaking due to the B-atom sublattice, the case of $f$-electron magnetism in $\mathrm{EuTi}{\mathrm{O}}_3$ is associated with $A$-sublattice symmetry breaking and its coupling to structural distortions. We find that (i) paramagnetic $cubic$ $\mathrm{EuTi}{\mathrm{O}}_3$ has an intrinsic tendency for both magnetic and positional symmetry breaking, while paramagnetic $tetragonal$ $\mathrm{EuTi}{\mathrm{O}}_3$ has only magnetic symmetry lowering and no noticeable positional symmetry lowering with respect to low-temperature antiferromagnetic tetragonal phase. (ii) Properly modeled paramagnetic tetragonal and cubic $\mathrm{EuTi}{\mathrm{O}}_3$ have a nonzero local magnetic moment on each Eu ion, consistent with the experimental observations of local magnetism in the para phases of $\mathrm{EuTi}{\mathrm{O}}_3$ significantly above the Néel temperature. Interestingly, (iii) the local positional distortion modes in the short-range ordered para phases are inherited from the long-range ordered low-temperature antiferromagnetic ground-state phase.

The $\mathrm{\Sigma }3\left\{112\right\}$ tilt grain boundary (GB) is found in many grains in bcc polycrystalline metals due to its low energy and high stability. Moreover, it is the coherent boundary of the $\left\{112\right\}$ twin. This paper studies the interaction of a pileup of $1/2\langle 111\rangle$ dislocations with the $\left\{112\right\}$ GB, extendable to the coherent $\left\{112\right\}$ twin boundary (TB). The results are applied to the interaction of the pileup of dislocations with the $\left\{112\right\}$ twin. The interacting dislocation is transformed into a GB dislocation (or TB dislocation) that acts as a source of disconnections responsible for the shear-coupled GB migration leading to twin growth or shrinkage when the interface is a TB. While a single dislocation cannot be transmitted through the interface, the stress field of the pileup facilitates the transmission if the tensile part of the dislocation core is closer to the interface than the compression part. The $\left\{112\right\}$ twin is found to create barriers to the motion of $1/2\langle 111\rangle$ crystal dislocations, and the strength of the barrier depends on crystallographic parameters. The results obtained in the slip-TB interaction prove that there is no transmission of dislocations through the twin. Thus, under twinning shear stress, all twins are strong obstacles for the glide of dislocations. Under antitwinnning shear stress, twins with thickness less than a few nanometers (5.6 nm in Fe) are annihilated by the interaction with a pileup of dislocations, contributing to softening, whereas thicker twins block the propagation of dislocations and confine dislocations inside the twin, which contributes to hardening.

Self-assembling patchy colloidal particles form a promising platform to create designer soft materials. To dress such systems with mechanical functionality, one can take inspiration from biological structures such as the cell's cytoskeleton, which consists of semiflexible filaments, whose mechanical behavior give the cell its unique mechanical properties. Here we present mechanical experiments on analogs of biological fibers, semiflexible “colloidal polymers” made from bonded patchy colloidal particles. We use optical tweezers to probe their extreme mechanics under increasingly high compressions and we reveal a rich nonlinear mechanical response involving buckling, viscoelastic creep, and ultimately break-up. We characterize and model this response using elastic and viscoelastic models involving Euler buckling and stress relaxation. This allows us to identify the critical Euler buckling force, and relate the critical bending at break-up to the finite patch size of the colloids. These results demonstrate the crucial role of the patch-patch interactions in the mechanics of self-assembled colloidal materials, and they provide mechanical relationships that are essential to design functional colloidal architectures inspired by nature.

We study the influence of fluorination on nucleation and growth of the organic parasexiphenyl molecule ($p$-6P) on amorphous silicon dioxide ($a\text{−}\mathrm{Si}{\mathrm{O}}_2$) by means of atomistically resolved classical molecular dynamics computer simulations. We use a simulation model that mimics the experimental deposition from the vapor and subsequent self-assembly onto the underlying surface. Our model reproduces the experimentally observed orientational changes from lying to upright standing configurations of the grown layers. We demonstrate that the increase in the number of fluorinated groups inside the $p$-6P leads to a smoother, layer-by-layer growth on the $a\text{−}\mathrm{Si}{\mathrm{O}}_2$ surface: We observe that in the first layers, due to strong molecule-substrate interactions the molecules first grow in chiral (fan-like) structures, where each consecutive molecule has a higher angle, supported by molecules lying underneath. Subsequently deposited molecules bind to the already standing molecules of the chiral structures until all molecules are standing. The growth of chiral islands is the main mechanism for growth of the fluorinated $p$-6P derivative, while the $p$-6P, due to the lower interaction with the underlying substrate, forms less chiral structures. The higher degree of chirality leads to a lower-energy barrier for step-edge crossing for the fluorinated molecules. We find that partial fluorination of the $p$-6P molecule can, in this way, significantly alter its growth behavior by modifying rough, three-dimensional growth into smooth, layer-by-layer growth. This has implications for the rational design of molecules and their functionalized forms, which could be tailored for a desired growth behavior and structure formation.

A multicomponent model that imposes conservation laws and constitutive relations for polymer chains, water, and ions was investigated by determining the transient changes in a negatively charged gel exposed to a solution containing both mono- and divalent cations. Association of ion exchange with gel volume is achieved by imposing a linear relation between the polymer-solvent interaction parameter and concentration of divalent cations adsorbed onto the polymer chains. Semiquantitative agreement with measurements made on sodium polyacrylate gels is demonstrated in three aspects: (1) dynamics of gel swelling and deswelling, (2) ion partitioning coefficient, and (3) effect of cross-link density. These results imply that the multicomponent coarse-grained continuum modeling approach can be useful for quantitative predictions over macroscopic length and timescales including the description of volume transitions exhibited by these systems.

Titanium nitride is an attractive material for a range of superconducting quantum-circuit applications owing to its low microwave losses, high surface inductance, and chemical stability. The physical properties and device performance, nevertheless, depend strongly on the quality of the materials. In this paper, we focus on the highly crystalline and epitaxial titanium nitride thin films deposited on sapphire substrates using magnetron sputtering at an intermediate temperature (${300}^{\circ }\mathrm{C}$). We performed a set of systematic and comprehensive material characterizations to thoroughly understand the structural, chemical, and transport properties. Microwave losses at low temperatures were studied using patterned microwave resonators, where the best internal quality factor in the single-photon regime is measured to be $3.3\times {10}^6$ and that in the high-power regime $>1.0\times {10}^7$. Adjusted with the material filling factor of the resonators, the microwave loss-tangent here compares well with the previously reported best values for superconducting resonators. This work lays the foundation of using epitaxial titanium nitride for low-loss superconducting quantum circuits.

Monolayer ${\mathrm{C}}_3\mathrm{N}$ is an emerging two-dimensional indirect band gap semiconductor with interesting mechanical, thermal, and electronic properties. In this paper we present a description of ${\mathrm{C}}_3\mathrm{N}$ electronic and dielectric properties, focusing on the so-called momentum-resolved exciton band structure. Excitation energies and oscillator strengths are computed in order to characterize bright and dark states, and discussed also with respect to the crystal symmetry. Activation of excitonic states is observed for finite transferred momenta: Indeed, we find an active indirect exciton at $\sim$ 0.9 eV, significantly lower than the direct optical gap of 1.96 eV, with excitonic binding energies in the range 0.6–0.9 eV for the lowest states. As for other 2D materials, we find a quasilinear excitonic dispersion close to $\mathrm{\Gamma }$, which however shows a downward convexity related to the indirect band gap of ${\mathrm{C}}_3\mathrm{N}$ as well as to the dark nature of the involved excitons.

We present a combined theoretical and experimental study of the electronic structure of stoichiometric ${\mathrm{Bi}}_4{\mathrm{Te}}_3$, a natural superlattice of alternating ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ quintuple layers and Bi bilayers. In contrast to the related semiconducting compounds ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ and ${\mathrm{Bi}}_1{\mathrm{Te}}_1$, density functional theory predicts ${\mathrm{Bi}}_4{\mathrm{Te}}_3$ is a semimetal. In this work, we compute the quasiparticle electronic structure of ${\mathrm{Bi}}_4{\mathrm{Te}}_3$ in the framework of the $GW$ approximation within many-body perturbation theory. The quasiparticle corrections are found to modify the dispersion of the valence and conduction bands in the vicinity of the Fermi energy, leading to the opening of a small indirect band gap. Based on the analysis of the eigenstates, ${\mathrm{Bi}}_4{\mathrm{Te}}_3$ is classified as a dual topological insulator with bulk topological invariants ${\mathbb{Z}}_2 (1;111)$ and magnetic mirror Chern number $n_M=1$. The bulk $GW$ results are used to build a Wannier-function-based tight-binding Hamiltonian that is further applied to study the electronic properties of the (111) surface. The comparison with our angle-resolved photoemission measurements shows excellent agreement between the computed and measured surface states and indicates the dual topological nature of ${\mathrm{Bi}}_4{\mathrm{Te}}_3$.

Topological quantum computing is based on the braiding of Majorana zero modes encoding topological qubits. A promising candidate platform for Majorana zero modes is semiconductor-superconductor hybrid nanowires. The realization of topological qubits and braiding operations requires scalable and disorder-free nanowire networks. Selective area growth of in-plane InAs and InSb nanowires, together with shadow-wall growth of superconductor structures, have demonstrated this scalability by achieving various network structures. However, the noticeable lattice mismatch at the nanowire-substrate interface, acting as a disorder source, imposes a serious obstacle along with this road map. Here, combining selective area and shadow-wall growth, we demonstrate the fabrication of PbTe-Pb hybrid nanowires—another potentially promising Majorana system—on a nearly perfectly lattice-matched substrate CdTe, all done in one molecular beam epitaxy chamber. Transmission electron microscopy shows the single-crystal nature of the PbTe nanowire and its atomically sharp and clean interfaces to the CdTe substrate and Pb overlayer, without noticeable interdiffusion or strain. The nearly ideal interface condition, together with the strong screening of charge impurities due to the large dielectric constant of PbTe, holds promise towards a clean nanowire system to study Majorana zero modes and topological quantum computing.

We report a comprehensive study of single crystals of the noncentrosymmetric rare-earth compound ${\mathrm{EuPtSi}}_3$ grown by the optical floating-zone technique. Measurements of the magnetization, ac susceptibility, and specific heat consistently establish antiferromagnetic order of localized ${\mathrm{Eu}}^{2+}$ moments below the Néel temperature $T_{\mathrm{N}}=17$ K, followed by a second magnetic transition at $T_{\mathrm{N}1}=16$ K. For a magnetic field along the easy [001] axis, the magnetic phase diagram is composed of these two phases. For fields applied in the magnetically hard basal plane, two additional phases emerge under magnetic field, where the in-plane anisotropy is weak with [100] being the hardest axis. At the phase transitions, the magnetic properties exhibit hysteresis and discrepancies between differential and ac susceptibility, suggesting slow reorientation processes of mesoscale magnetic textures. Consistently, powder and single-crystal neutron diffraction in zero field identify magnetic textures that are modulated on a length scale of the order of $100\text{Å}$, most likely in the form of Néel-type antiferromagnetic cycloids.

Layered ruthenium oxyfluorides have various crystal structures and Ru oxidation states and exhibit unique physical properties. While various layered ruthenates have reportedly been topochemically fluorinated with Sr as $A$ sites, investigation of the fluorination of layered ruthenates containing smaller Ca ions is lacking. In this paper, we fabricated phase-pure and single-crystalline thin films of ${\mathrm{Ca}}_2{\mathrm{RuO}}_{2.5}{\mathrm{F}}_2$ on ${\mathrm{LaSrAlO}}_4$ (001) substrates via topochemical fluorination of the ${\mathrm{Ca}}_2{\mathrm{RuO}}_4$ precursor using polyvinylidene fluoride. The obtained fluorinated thin films had a chemical composition of ${\mathrm{Ca}}_2{\mathrm{RuO}}_{2.5}{\mathrm{F}}_2$ with the ${\mathrm{Ru}}^{3+}$ state, as determined by energy-dispersive x-ray spectroscopy and x-ray photoemission spectroscopy, whereas the film prepared via ${\mathrm{Sr}}_2{\mathrm{Ru}}^{4+}{\mathrm{O}}_4$ fluorination had a composition of ${\mathrm{Sr}}_2{\mathrm{Ru}}^{4+}{\mathrm{O}}_3{\mathrm{F}}_2$. Scanning transmission electron microscopy revealed that ${\mathrm{Ca}}_2{\mathrm{RuO}}_{2.5}{\mathrm{F}}_2$ has only 1 ${\mathrm{F}}^{-}$ site in CaO rock-salt blocks, whereas ${\mathrm{Sr}}_2{\mathrm{RuO}}_3{\mathrm{F}}_2$ has two inequivalent ${\mathrm{F}}^{-}$ sites in the SrO layers. The ${\mathrm{Ca}}_2{\mathrm{RuO}}_{2.5}{\mathrm{F}}_2$ film was insulating, with a resistivity (ρ) of $8.6\times {10}^{-2}\mathrm{\Omega }\mathrm{cm}$ at 300 K. Moreover, the temperature behavior of ρ was well described by the two-dimensional variable range hopping model. These results demonstrate that local distortion is an important factor that governs the topochemical fluorination of ruthenates and affects the crystal and electronic structures of the reactants.

Semilocal density-functional theory (DFT) methods exhibit significant errors for the phase diagrams of transition-metal oxides that are caused by an incorrect description of molecular oxygen and the large self-interaction error in materials with strongly localized electronic orbitals. Empirical and semiempirical corrections based on the $\mathrm{DFT}+U$ method can reduce these errors, but the parameterization and validation of the correction terms remains an on-going challenge. We develop a systematic methodology to determine the parameters and to statistically assess the results by considering interlinked thermochemical data across a set of transition metal compounds. We consider three interconnected levels of correction terms: (1) a constant oxygen binding correction, (2) Hubbard-$U$ correction, and (3) $\mathrm{DFT}/\mathrm{DFT}+U$ compatibility correction. The parameterization is expressed as a unified optimization problem. We demonstrate this approach for $3d$ transition metal oxides, considering a target set of binary and ternary oxides. With a total of 37 measured formation enthalpies taken from the literature, the dataset is augmented by the reaction energies of 1710 unique reactions that were derived from the formation energies by systematic enumeration. To ensure a balanced dataset across the available data, the reactions were grouped by their similarity using clustering and suitably weighted. The parameterization is validated using leave-one-out cross validation (CV), a standard technique for the validation of statistical models. We apply the methodology to the strongly constrained and appropriately normed (SCAN) density functional. Based on the CV score, the error of binary (ternary) oxide formation energies is reduced by 40% (75%) to 0.10 (0.03) eV/atom. A simplified correction scheme that does not involve $\mathrm{SCAN}/\mathrm{SCAN}+U$ compatibility terms still achieves an error reduction of 30% (25%). The method and tools demonstrated here can be applied to other classes of materials or to parameterize the corrections to optimize $\mathrm{DFT}+U$ performance for other target physical properties.

Solute strengthening is an important mechanism that contributes to improving the mechanical properties of alloys and particularly the recent generations of concentrated alloys. The stress field emerging from an elastic model of a random solid solution displays strongly anisotropic correlations that interact differently with dislocations of different characters. In the present paper, we investigate the depinning transition of edge and screw dislocations evolving in such a correlated stress environment using a dislocation dynamics numerical model. We find that edge dislocations are only weakly affected by the correlations, while screw dislocations are strongly influenced, showing a smaller critical stress, which increases with the amplitude of the stress noise with a larger exponent than the edge dislocation. The numerical results are compared with existing statistical models of solute strengthening, allowing to discuss critically their assumptions.

${\mathrm{Cu}}_2{\mathrm{ZnSnS}}_4$ (CZTS) is an earth-abundant photovoltaic absorber material predicted to provide a sustainable solution for commercial solar applications. However, the efficiency of such solar cells is rather limited, cation disorder being often designated as the culprit. Raman spectroscopy has been widely used to characterize CZTS. Nonetheless, the interpretation of the spectra in terms of the atomic-scale disorder is precluded by the lack of consensus between theoretical and experimental results. In particular, there is a strong discrepancy in the relative intensities of the two prominent $A$ phonon peaks of the spectra. In the present study, we demonstrate that the internal parameters characterizing the position of the S atoms strongly influence these intensities. We show that agreement with experiments can be completely recovered when adopting the geometry computed using a hybrid exchange-correlation functional. Finally, using special quasirandom structures, we demonstrate that the disorder only leads to a change of the shape of the Raman peaks (tailing or leading edges, shouldering and splitting). This could be exploited to assess the quality of the sample in terms of how ordered they are.

Using an atomistic approach, we predict the emergence of hybrid quasiparticles, namely, domain-wall-induced electromagnons, that arise from dynamical couplings between magnons and optical phonons in systems possessing ferroelectric domain walls. These quasiparticles induce THz resonances in magnetoelectric responses and preferentially localize either near the domain walls or near the middle of domains. Such behavior is explained through dispersion analysis that allows us to track the emergent multidomain excitations back to single-domain magnetoelectric (ME) modes. The latter, scattered by a periodic array of domain walls, are shown to endow the domain-wall-induced electromagnons with a mixed localized mode and standing- or propagating-wave characters. Such features can be exploited to reach strikingly large ME conversion and design more reliable and ultrafast ME devices with less energy consumption and using, e.g., local probes.