Development of nano-meter multilayered magnetic film with super low energy loss and application for electric motor

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The multilayered magnetic ring-type core was made by a facing-target-type RF magnetron sputtering system and the magnetic energy loss was measured. The energy loss vs. drive frequency curve showed the peak at about 200 kHz in the condition of constant magnetic field because of the resonance of magnetic domain-wall. It was found that the resonance frequency shifted toward higher values with increasing the amplitude of magnetic drive field and the peak collapse happened. This phenomenon was coincident with the prediction of chaos theory for magnetic energy loss proposed by H.Okuno. It was found that the magnetic domain-wall showed very complicated motion with a continuous power spectrum. The fractal structure in the reconstructed attractor was found by the method of recurrence plot and the irregular domain-wall motion was certified to be the chaos in the deterministic system and not the randomness such as the noise in the stochastic system. The general evaluation was performed by using the correlation-dimension analysis, the map of chaos region, the method of controlling chaos and the magnetic energy loss. With the non-integral number of 8.83 for correlation-dimension, the irregular domain-wall motion was certainly proved to be the chaos. The chaotic domain-wall motion was found to exist in the region except large amplitude-high frequency or small amplitude-low frequency of drive field and the border near the bottom of chaos region was found to be made by the region of domain-wall resonance. The half period extended delayed feedback control method was developed to control the chaotic domain-wall motion, which showed the best controllability and the least magnetic energy loss. The above results were presented in the international conference. The proposed chaos theory of magnetic energy loss and the control method of decreasing it underwent an evaluation.