Study on multi-stage kinetics and main dissipation interval of magnetization reversal of nanocrystalline alloys under high-frequency excitation

To quantify the time-domain concentration of hysteretic dissipation in FINEMET-type nanocrystalline alloys, a three-dimensional amorphous/nanocrystalline micromagnetic model is developed under prescribed sinusoidal magnetic-field excitation. The model is validated against measured static magnetic properties and dynamic hysteresis-loop areas in the 1–20 kHz range. The magnetization reversal half-cycle is segmented into five stages for time-domain analysis: initial stability, energy pre-accumulation and magnetization relaxation, domain nucleation and early expansion, domain-wall-dominated rapid reversal, and saturation approaching with structural adjustment. These stages correspond to established micromagnetic processes and are used to correlate magnetization, magnetization rate, domain evolution, energy terms, and damping-related dissipation. A q -dependent main dissipation interval ( q -MDI) is introduced as the shortest time interval in which a prescribed fraction q of the half-cycle dissipated energy is accumulated. The representative 60%-MDI and threshold-sensitivity results indicate that the most concentrated dissipation occurs mainly near the transition from domain nucleation to rapid domain-wall propagation. Within the present equivalent model, increasing field amplitude produces a model-dependent transition near 28 mT, while increasing frequency shifts the 60%-MDI toward earlier stages of the half-cycle and gradually stabilizes its location. These results provide guidance for material-level micromagnetic analysis and microstructure-informed design of nanocrystalline soft magnetic alloys.