Dense microwave dielectric ceramics of Ce₂[Zr_1−x(Al_1/2Ta_1/2)_x]₃(MoO₄)₉ (CZMAT) (x = 0.02–0.10) were prepared by the conventional solid-state route. The effects of (Al_1/2Ta_1/2)⁴⁺ on their microstructures, sintering behaviors, and microwave dielectric properties were systematically investigated. On the basis of the X-ray diffraction (XRD) results, all the samples were matched well with Pr₂Zr₃(MoO₄)₉ structures, which belonged to the space group $$R\bar 3c$$R 3 ¯ c . The lattice parameters were obtained using the Rietveld refinement method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips—Van Vechten—Levine (P—V—L) theory. Excellent dielectric properties of Ce₂[Zr_0.94(Al_1/2Ta_1/2)_0.06]₃(MoO₄)₉ with a relative permittivity (ε_r) of 10.46, quality factor (Q × f) of 83,796 GHz, and temperature coefficient of resonant frequency (τ_f) of −11.50 ppm/°C were achieved at 850 °C.

Altermagnets, a recently identified class of collinear magnets, exhibit unique properties such as zero net magnetization and spin polarization dictated by lattice symmetry, making them a subject of intense research. In contrast to conventional strategies for inducing altermagnetism in antiferromagnets that rely on manipulating real‐space symmetry, this work introduces a novel and general approach to achieving altermagnetism by modulating spin‐space symmetry. Through a combination of tight‐binding models and first‐principles calculations, the microscopic origin of altermagnetism driven by spin‐space symmetry is uncovered, and the mechanism underlying enhanced spin splitting is identified. Furthermore, it is demonstrated that this spin‐space modulation can synergistically interact with ferroelectricity, enabling a spin symmetry‐dependent magnetoelectric coupling mechanism that is distinct from conventional multiferroics. This unique coupling is validated by the magneto‐optical Kerr effect, providing a robust theoretical foundation for the development of next‐generation spintronic devices that harness the potential of altermagnetism.