Spatially Gradient Properties in High‐Frequency Ferrites via Single‐Mode Microwave Processing

Herein, spatial tailoring of microstructure, magnetic, and mechanical properties in high‐frequency Ni–Zn ferrite toroidal core over cm‐length scales via an efficient microwave (MW) processing technique is successfully achieved. Depending on gradient processing conditions, one region in a sample (R1) is more efficiently being heated than the other region (R2) due to the spatial variation in losses. The controlled variation of grain sizes (D), saturation magnetization (M_S), and microhardness traverses from 0.42 to 2.25 μm, 28 to 76 emu g⁻¹, and 84 to 162 HV, respectively from the R2 to R1. Moreover, the experimentally observed spatially gradient ferrite processing in a single‐mode electric (E)‐field MW cavity is validated with simulation results using finite element modeling. This concept of functionally graded material properties can be an interesting and feasible pathway toward improving performances of a wide range of functional ceramics and related devices, including soft magnetic ferrite materials in power magnetic devices such as transformers and inductors.