分类： 材料科学 >> 电子、光学、磁材料 提交时间： 2023-03-01
摘要： The intrinsic high frequency permeability spectra of ferromagnetic composites containing different volume fractions of iron and cobalt have been simulated. A law (called Mghans law) is proposed to explain the simulated results by assuming that there are plenty of LLG (Landau-Lifshitz-Gilbert) type natural resonances contributing to the intrinsic permeability spectra. The results clearly show that the spectra strongly depend on the distribution of local effective magnetic field, the interaction between the magnetic particles, the inhomogeneous damping constant of LLG precession, and the initial equilibrium states. Especially, the effect of particles shape distribution in each sampling on the local effective magnetic field. In view of this fact: it is absolutely impossible to have the same effect from these factors when someone prepares several measurement samples, an uncertainty principle is believed to hold for measuring the intrinsic permeability of an electromagnetic (EM) composite. Therefore, this law tells us that it should be cautious when comparing or evaluating the EM properties of composites (for instance, EM wave absorbing composites). Memory effect can be used to restore the intrinsic high frequency permeability for a specific defunct composite sample.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2021-12-14
摘要： 与单根Fe纳米线的GHz磁导率相比较，我们对具有L10型晶体结构的FePt纳米线在处于剩余磁化状态下（Mr/Ms=1.0）的太赫兹磁导率进行了微磁学仿真。由于FePt纳米线具有很强的磁晶各向异性场，我们的研究表明它可以在0.348THz下具有很强的太赫兹磁导率，这曾被认为只能通过人工超材料才能获得。L10-FePt纳米线的THz磁谱明显不同于Fe纳米线GHz下的磁谱，它存在不同寻常的负数磁导率虚部(u"<0)，我们认为这与它不寻常自然共振下的旋进过程所导致的等效负数阻尼系数相关。
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