| Research Abstract |
In soft magnetic materials, the induced preferred directions within the domain wall often creates localized potential minima. As these minima become deeper with time, the mobility of the domain wall will decrease, associated with gradual decrease of initial permeability after demagnetization, so called, disaccommodation (DA). For the purpose of applying this phenomenon to the problem of mechanical shock in the process of occlusion or a functional pressure we observed an occurrence of DA and relation between DA and the strength of the shock in not only bulk single crystals of magnetic garnet such as yttrium iron garnets and spinel ferrites we observed for the first time, but also bulk polycrystalline sintered samples or single crystalline epitaxially grown thin films. The basic concept of our experiment is as follows. Although some loadings are static, any other ones are dynamic ; that is, they vary with time or an impact loading. A typical example could be caused by the collision of objects. When the block (m=100 g) is released from rest, it falls a distance h, then the impact loading is proportional to the quantity of the summation of mh and the square root of mh. We found the increase of the permeability in these single crystalline samples tends to be proportional to the quantity. In polycrystalline samples, the issue becomes yet further complicated due to the microstructure, which has been cleared from the many SEM photographs. The measurements of the impact loadings, with a strain-gauge-method were carried out. They are very complicated so that the oscillating parts of the signals are involved.
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