This paper presents a new loss computation method for soft magnetic composite (SMC), which allows us to evaluate the loss for wide operating conditions. A formula for evaluation of eddy current and hysteresis losses is introduced. The effective volume fraction of the magnetic grain is determined from the sampled measured data. It is shown that the formula provides accurate estimate of the total loss in a toroidal SMC core. Moreover, the loss of SMC inductor is shown to be also accurately evaluated at small computational burden using the proposed method.
It is revealed that contact of magnetic particles in soft magnetic composite (SMC) significantly increases the macroscopic permeability. It is shown that Ollendorff's formula which assumes homogenous magnetic particles and insulation layers underestimates the macroscopic permeability of SMC. It is suggested that the excess in the permeability is due to the local contacts among the magnetic particles. The effect of the magnetic contact is evaluated using a magnetic circuit model.
We theoretically investigate the magnetotransport of Dirac fermions coupled with localized moments to understand the physical properties of the Dirac material EuMnBi 2 . Using an interlayer hopping form, which simplifies the complicated interaction between the layers of Dirac fermions and the layers of magnetic moments in EuMnBi 2 , the theory reproduces most of the features observed in this system. The hysteresis observed in EuMnBi 2 can be caused by the valley splitting that is induced by the spin-orbit coupling and the external magnetic field with the molecular field created by localized moments. Our theory suggests that the magnetotransport in EuMnBi 2 is due to the interplay among Dirac fermions, localized moments, and spin-orbit coupling.
Three novel organic conductors (TMTSF)8(I3)5, (TMTSF)5(I3)2, and (TMTSF)4(I3)4·THF (THF = tetrahydrofuran) were synthesized and their crystal structures were characterized by X-ray diffraction analyses, where TMTSF denotes tetramethyltetraselenafulvalene. The crystals of both the (TMTSF)8(I3)5 and (TMTSF)5(I3)2 are composed of one-dimensional stacks of TMTSF trimers separated by TMTSF monomers. The crystal of the (TMTSF)4(I3)4·THF is composed of the TMTSF tetramers and I3− tetramers; and regarded as the elongated rock-salt structure. The electrical conductivity of the (TMTSF)8(I3)5 and (TMTSF)5(I3)2 is about 60 and 50 S·cm−1 at room temperature, respectively. The electrical resistivity of (TMTSF)8(I3)5 is weakly metallic below room temperature and rapidly increases below 88 and 53 K on cooling suggesting two possible phase transitions. The electrical resistivity of (TMTSF)5(I3)2 is semiconducting below room temperature but shows an anomaly around 190 K, below which the activation energy becomes small. The application of hydrostatic pressure up to 1.7 GPa do not change these behaviors of (TMTSF)8(I3)5 and (TMTSF)5(I3)2 very much. A method to evaluate the non-integer valence of crystallographically independent TMTSF molecules is developed by using the DFT (density-functional-theory) and MP2 (Hartree–Fock calculations followed by Møller–Plesset correlation energy calculations truncated at second order) calculations. It is shown that the method gives the valence of the TMTSF molecules of the I3 salts consistent with their electrical properties.
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