| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 90 === Ferromagnetic materials have been widely used in recording devices, actuators, and sensors owing to inherent hysteresis and magnetostriction. As a result, the investigation of interaction between hysteresis and stress induced by magnetostriction has been studied extensively in current literature.
This article has developed a framework based on micromagnetics, together with the famous Landau-Lifshitz-Gilbert equation and boundary element method, to study the effect of the internal stress induced by magnetostriction and external magnetic field and mechanical loading on the magnetic domain rearrangement. Our method is different form the traditional one proposed in literatures, which simply replaces the total strain by spontaneous strain. As a result, it is questionable that the strain compatibility condition can be satisfied by this approximation. Further, the effect of internal stress due to incompatible strain on the rearrangement of magnetic domains is not taken into account. On the other hand, we have proposed a modified boundary element method which conforms to the compatibility condition and is able to compute the internal stress and the corresponding effective magnetic field accurately. Our results have shown that for ferromagnetic crystals with sopnstaneous strain around 10-5 order of magnitude, the difference between the traditional approximate method and ours is small. In addition, the influence of the internal stress on magnetic domains is also not significant. However, we have demonstrated that for ferromagnetic crystals with spontaneous strain around 10-3 order of magnitude such as Terfenol-D, the traditional approximate method to study the effect of stress on magnetic domains is questionable, and the effective magnetic field due to internal stress cannot be ignored.
Key words: micromagnetics, BEM, hysteresis, magneostriction
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