Abstract:Magnetoelectric phenomena are intimately linked to relativistic effects and also require the material to break spatial inversion symmetry and time-reversal invariance. Magnetoelectric coupling can substantially affect light–matter interaction and lead to non-reciprocal light propagation. Here, we confirm on a fully experimental basis, without invoking either symmetry-based or material-specific assumptions, that the optical magnetoelectric effect in materials with non-parallel magnetization (M) and electric pol… Show more
“…The vacuum slab was constructed with a 15-Å vacuum, and the structure was fully minimized until the final energy differences were below 1 meV. The final magnetic moments of Co and Fe atoms in all of the intermediate structures were confirmed to have high-spin states with the antiferromagnetic arrangements (Figure S15) of T d and O h sites in accordance with the previous studies. , …”
Section: Materials
and Methodssupporting
confidence: 82%
“…The final magnetic moments of Co and Fe atoms in all of the intermediate structures were confirmed to have high-spin states with the antiferromagnetic arrangements (Figure S15) of T d and O h sites in accordance with the previous studies. 59,60 Oxygen evolution mechanisms in Figures 5a and S12 are based on the AEM and the LOM as follows, and the thermodynamics were calculated by the computational hydrogen electrode model. 61 AEM under alkaline conditions ■ AUTHOR INFORMATION…”
Oxygen evolution reaction (OER) plays a crucial role as a counter half-reaction for both electrochemical hydrogen production through water splitting and the generation of valuable carbon compounds via CO 2 reduction. To overcome the sluggish kinetics of the OER, significant efforts have been devoted to developing cost-effective, sustainable, and efficient electrocatalysts, with transition-metal-based catalysts emerging as promising candidates. Herein, we successfully synthesized a core−shell type nanostructure of Fe-doped CoMoO x /CoMoO x (CMFO), which exhibits excellent electrocatalytic properties for OER. The presence of an amorphous layer of Fe-doped CoMoO x with abundant oxygen vacancies, along with the stability of a key OER intermediate, *O, contributes to the enhanced activity of CMFO catalyst compared to pristine CoMoO x (CMO). The optimized catalyst of CMFO-550 achieved much lower overpotential and Tafel slope and also exhibited better remarkable long-term stability for over 90 h compared to CMO-550. These findings highlight the potential of CMFO-550 as a cost-effective and highly efficient electrocatalyst for the OER. The successful development of this core−shell nanostructure opens up a new opportunity for the design and synthesis of advanced electrocatalysts for the OER, with implications for various applications in energy conversion and storage.
“…The vacuum slab was constructed with a 15-Å vacuum, and the structure was fully minimized until the final energy differences were below 1 meV. The final magnetic moments of Co and Fe atoms in all of the intermediate structures were confirmed to have high-spin states with the antiferromagnetic arrangements (Figure S15) of T d and O h sites in accordance with the previous studies. , …”
Section: Materials
and Methodssupporting
confidence: 82%
“…The final magnetic moments of Co and Fe atoms in all of the intermediate structures were confirmed to have high-spin states with the antiferromagnetic arrangements (Figure S15) of T d and O h sites in accordance with the previous studies. 59,60 Oxygen evolution mechanisms in Figures 5a and S12 are based on the AEM and the LOM as follows, and the thermodynamics were calculated by the computational hydrogen electrode model. 61 AEM under alkaline conditions ■ AUTHOR INFORMATION…”
Oxygen evolution reaction (OER) plays a crucial role as a counter half-reaction for both electrochemical hydrogen production through water splitting and the generation of valuable carbon compounds via CO 2 reduction. To overcome the sluggish kinetics of the OER, significant efforts have been devoted to developing cost-effective, sustainable, and efficient electrocatalysts, with transition-metal-based catalysts emerging as promising candidates. Herein, we successfully synthesized a core−shell type nanostructure of Fe-doped CoMoO x /CoMoO x (CMFO), which exhibits excellent electrocatalytic properties for OER. The presence of an amorphous layer of Fe-doped CoMoO x with abundant oxygen vacancies, along with the stability of a key OER intermediate, *O, contributes to the enhanced activity of CMFO catalyst compared to pristine CoMoO x (CMO). The optimized catalyst of CMFO-550 achieved much lower overpotential and Tafel slope and also exhibited better remarkable long-term stability for over 90 h compared to CMO-550. These findings highlight the potential of CMFO-550 as a cost-effective and highly efficient electrocatalyst for the OER. The successful development of this core−shell nanostructure opens up a new opportunity for the design and synthesis of advanced electrocatalysts for the OER, with implications for various applications in energy conversion and storage.
“…At first, we verify by susceptibility measurements that the layered crystal structure of Co 2 Mo 3 O 8 leads to strong magnetic anisotropies and confines the dominant exchange paths to individual honeycomb layers, as implied by the lack of dispersion of the magnon branches along the c axis [47]. Indeed, we find a large difference between the susceptibility values obtained for fields parallel and perpendicular to the layers.…”
Section: Spin Model Of Adjacent Antiferro-and Ferrimagnetic Layerssupporting
Ferro/ferri- and antiferromagnetic orders are typically exclusive in nature, thus, their co-existence in atomic-scale proximity is expected only in heterostructures. Breaking this paradigm and broadening the range of unconventional magnetic states, we report here on the observation of a new, atomic-scale hybrid spin state. This ordering is stabilized in three-dimensional crystals of the polar antiferromagnet Co$_2$Mo$_3$O$_8$ by magnetic fields applied perpendicular to the \emph{Co} honeycomb layers and possesses a spontaneous in-plane ferromagnetic moment. Our microscopic spin model, capturing the observed field dependence of the longitudinal and transverse magnetization as well as the magnetoelectric/elastic properties, reveals that this novel spin state is composed of an alternating stacking of antiferromagnetic and ferrimagnetic honeycomb layers. The strong intra-layer and the weak inter-layer exchange couplings together with competing anisotropies at octahedral and tetrahedral \emph{Co} sites are identified as the key ingredients to stabilize antiferromagnetic and ferrimagnetic layers in such close proximity. We show that the proper balance of magnetic interactions can extend the stability range of this hybrid phase down to zero magnetic field. The possibility to realize a layer-by-layer stacking of such distinct spin orders via suitable combinations of microscopic interactions opens a new dimension toward the nanoscale engineering of magnetic states.
Magnetic order in most materials occurs when magnetic ions with finite moments arrange in a particular pattern below the ordering temperature. Intriguingly, if the crystal electric field (CEF) effect results in a spin-singlet ground state, a magnetic order can still occur due to the exchange interactions between neighboring ions admixing the excited CEF levels. The magnetic excitations in such a state are spin excitons generally dispersionless in reciprocal space. Here we use neutron scattering to study stoichiometric Ni2Mo3O8, where Ni2+ ions form a bipartite honeycomb lattice comprised of two triangular lattices, with ions subject to the tetrahedral and octahedral crystalline environment, respectively. We find that in both types of ions, the CEF excitations have nonmagnetic singlet ground states, yet the material has magnetic order. Furthermore, CEF spin excitons from the tetrahedral sites form a dispersive diffusive pattern around the Brillouin zone boundary, likely due to spin entanglement and geometric frustrations.
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