Tailored dopant strategies are proposed to optimise the energy density of BiFeO ₃ –SrTiO ₃ , which can be adapted for other high polarisability oxide-based systems.

Spin-orbit coupled honeycomb magnets with the Kitaev interaction have received a lot of attention due to their potential of hosting exotic quantum states including quantum spin liquids. Thus far, the most studied Kitaev systems are 4d/5d-based honeycomb magnets. Recent theoretical studies predicted that 3d-based honeycomb magnets, including Na₂Co₂TeO₆ (NCTO), could also be a potential Kitaev system. Here, we have used a combination of heat capacity, magnetization, electron spin resonance measurements alongside inelastic neutron scattering (INS) to study NCTO’s quantum magnetism, and we have found a field-induced spin disordered state in an applied magnetic field range of 7.5 T < B (⊥ b-axis) < 10.5 T. The INS spectra were also simulated to tentatively extract the exchange interactions. As a 3d-magnet with a field-induced disordered state on an effective spin-1/2 honeycomb lattice, NCTO expands the Kitaev model to 3d compounds, promoting further interests on the spin-orbital effect in quantum magnets.

The structure and thermoelectric (TE) properties of La-doped, A-site-deficient SrTiO₃ (Sr_1–3x/2La_xTiO₃) ceramics sintered in air and N₂/5% H₂ have been investigated. Air-sintered ceramics with 0.10 ≤ x < 0.30 appear cubic by X-ray diffraction (XRD) but exhibit superstructure consistent with a tetragonal cell (a⁰a⁰c^–), according to electron diffraction (ED) studies. 0.30 ≤ x < 0.50 have additional short-range A-site vacancy (V_A) ordering, and x ≥ 0.50 are orthorhombic with an a^–a^–c⁺ tilt system and long-range V_A ordering. 0.10 ≤ x ≤ 0.50 reduced in N₂/5% H₂ are oxygen-deficient and appear cubic in XRD patterns but exhibit superstructure compliant with an a⁰a⁰c^– tilt system by ED. For x = 0.50, additional short-range V_A order is observed, and x > 0.50 are orthorhombic with an a^–a^–c⁺ tilt system and long-range V_A ordering. x = 0.15 sintered in N₂/5% H₂ shows the largest dimensionless TE figure-of-merit ZT = 0.41 at 973 K reported for n-type SrTiO₃-based ceramics, suggesting that the accommodation of La through formation of (V_Sr) coupled with reduction in N₂/5% H₂ represents a new protocol for the development of oxide-based thermoelectrics.

An external magnetic field can induce a transition in $\alpha \text{−}{\mathrm{RuCl}}_3$ from an ordered zigzag state to a disordered state that is possibly related to the Kitaev quantum spin liquid. Here, we present field-dependent inelastic neutron scattering and magnetocaloric effect measurements implying the existence of an additional transition out of the quantum spin-liquid phase at an upper field limit $B_u$. The neutron scattering shows three distinct regimes of magnetic response. In the low-field ordered state the response shows magnon peaks; the intermediate-field regime shows only continuum scattering, and above $B_u$ the response shows sharp magnon peaks at the lower bound of a strong continuum. Measurable dispersion of magnon modes along the $(0,0,L)$ direction implies non-negligible interplane interactions. Combining the magnetocaloric effect measurements with other data, a $T\text{−}B$ phase diagram is constructed. The results constrain the range where one might expect to observe quantum spin-liquid behavior in $\alpha \text{−}{\mathrm{RuCl}}_3$.

To meet the United Nations' sustainable development goal of affordable and clean energy, there has been a growing need for low-cost, green, and safe energy storage technologies. High-field and energy-density capacitors have gained substantial attention from academics and industry, particularly for power electronics, where they will play a key role in optimising the performance of management systems in electric vehicles. The key figure of merit, energy density (W_rec), for high-field applications has dramatically increased year-on-year from 2020 to 2024, as evidenced by over 250 papers, demonstrating ever larger W_rec values. This review briefly introduces the background and principles of high energy density ceramics, but its focus is to provide constructive and comprehensive insight into the evaluation of W_rec, E_max, ΔP, and η, and more importantly, the normalised metrics, W_rec/E_max and W_rec/ΔP in lead-free dielectric ceramics. We also present several optimisation strategies for materials modification and process innovation that have been recently proposed before providing perspectives for the further development of high-field and high-energy density capacitors.

Magnetization plateaus in quantum magnets—where bosonic quasiparticles crystallize into emergent spin superlattices—are spectacular yet simple examples of collective quantum phenomena escaping classical description. While magnetization plateaus have been observed in a number of spin-1/2 antiferromagnets, the description of their magnetic excitations remains an open theoretical and experimental challenge. Here, we investigate the dynamical properties of the triangular-lattice spin-1/2 antiferromagnet Ba₃CoSb₂O₉ in its one-third magnetization plateau phase using a combination of nonlinear spin-wave theory and neutron scattering measurements. The agreement between our theoretical treatment and the experimental data demonstrates that magnons behave semiclassically in the plateau in spite of the purely quantum origin of the underlying magnetic structure. This allows for a quantitative determination of Ba₃CoSb₂O₉ exchange parameters. We discuss the implication of our results to the deviations from semiclassical behavior observed in zero-field spin dynamics of the same material and conclude they must have an intrinsic origin.