An ultrahigh electric field–induced strain of 0.9% (under 1 kV mm ⁻¹ ) is achieved in lead-free ferroelectric crystals.

We investigate narrowband transmission filters based on subwavelength-grating reflectors at normal incidence. Computational results show that the filtering is realized through symmetry-protected mode coupling. The guided mode resonances introduced by the slab layer allow flexible control of the filter frequencies. The quality factor of the filters could exceed 10⁶. Dielectric gratings can be used over the entire range of electromagnetic waves, owing to their scale-invariant operations. Owing to the high refraction index and low index dispersion of semiconductors in the infrared range, these filters can be applied over a broad range from near infrared to terahertz frequencies.

Exploring the performance of nanoscale multiferroic materials is a significant challenge because the physical properties of these materials vary dramatically on this scale. In the present work, BiFeO₃ (BFO) nanoparticles are synthesized by a facile sol-gel method, producing homogeneous spherical nanoparticles whose Raman modes and binding energies coincide with pure rhombohedral perovskite BFO. The dramatic magnetic properties of nanoscale BFO with diameters in the range of 50–130 nm are explored by analyzing the temperature and field dependence of magnetization, and detailed zero-field cooling and field cooling magnetization curves show that interparticle interactions play a constructive role in increasing the magnetic response. Moreover, BFO nanoparticles have two absorption regions in the range of 2–18 GHz, and the minimum reflection loss is −18 dB. The finite-size effect is discussed as the primary mechanism for enhancing the ferromagnetism and microwave absorption, and the results provide a feasible route for designing multifunctional materials.