Characterization and assessment of the wideband magnetic properties of nanocrystalline alloys and soft ferrites

Abstract

Abstract

Correlation between Cutting Clearance, Deformation Texture, and Magnetic Loss Prediction in Non-Oriented Electrical Steels

“…While the distribution of the local coercive fields in the sample of 3% cutting clearance with the lowest W(f ) response is quite close to the uniform one-i.e., Γ(H c ) ∝ H c −0.08 ≈ 1-the anomalous increase of W(f ) in the annealed samples of higher cutting clearance at high frequencies can be understood in terms of nonuniform distribution function Γ(H c ) ∝ H c −0.8 . It is supported by the equivalent behaviour found in soft magnetic alloys and ferrites [40].…”

“…Figure 11b,d in different frequency representation). The loss behaviour different from W exc ∝ f 1/2 well inside the skin-effect-free region suggests the distortion of the uniform distribution of local pinning fields Γ(H c ) [40]. Considering the non-uniform distribution of the type Γ(H c ) ∝ H c n−1 with 0 < n ≤ 1 (reducing to the uniform distribution for n = 1) and the fundamental correlation between hysteresis and excess loss, the generalized expression translating the W hyst into W exc , can be worked out as…”

The temperature dependence of magnetic losses in CoO-doped Mn-Zn ferrites

“…2) and β sd = (2J s /μ 0 γδ)⋅α, with δ the dw thickness. It turns out that in the Mn-Zn ferrites, β eddy ( β sd 17 and spin damping can be taken as the sole significant dissipation mechanism for the moving domain walls. We can then conclude that the dw generated dynamic loss in Mn-Zn ferrites can be given fairly similar treatment as in steel sheets, but for the involved damping mechanism, and one can still invoke the statistical properties of the local coercive fields in regulating the unfolding of the dw processes under increasing magnetizing frequencies.…”

“…This is done according to the basic statements of the Statistical Theory of Losses (STL), which are extended to cover the loss phenomenology over a very large range of frequencies in the insulating/semi-insulating sintered ferrites. 16,17 In this way, we overcome the limited predicting ability of the standard approach to the energy losses in Mn-Zn ferrites, based on the identification and combination of quasistatic W h , eddy current W e , and residual W r losses. 10,14,18,19 Of these components, only W e is calculated, in general, making use of a classical Maxwellian formulation and neglecting the actual structural and magnetic heterogeneity of the material.…”

“…By the generalized STL, we provide a comprehensive interpretative framework, where, while accounting for the actual heterogeneous structure of the sintered ferrites, we recognize the separate contributions of domain wall (dw) displacements and rotations to the magnetization process, with the associated dissipation channels provided by eddy currents and spin damping. 16,17,20 In this work, we have investigated the temperature dependence of the magnetic properties of Mn-Zn ferrites obtained by sintering at T = 1325 °C, subjected to conventional doping by CaO and Nb 2 O 5 and additional doping by CoO, in quantities ranging between 0 and 6000 ppm. Permeability and energy losses have been measured, at different values of the peak polarization J p, up to 1 GHz and at temperatures ranging between -20 °C and 130 °C.…”