Magnetic losses versus sintering treatment in Mn-Zn ferrites

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

“…with C a constant. The experimental rotational permeability components 'rot(f) and ''rot(f), independent on Jp up to Jp = 0.1Js -0.2 Js, are extracted from the measured permeability by means of a self-consistent procedure, discussed in [49]. This is based on the idea that at low frequencies no rotational contribution to ''(f) can occur.…”

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

“…We have recently shown that an estimate of ⟨K eff ⟩ can be made in sintered ferrites, by extracting the contribution of the rotational magnetization processes from the value of the low-field DC permeability. 16 Applied to the present experiments on Co-doped Mn-Zn ferrites, this feature permits us to verify that optimal addition of CoO = 3000-4000 ppm leads to smoothed dependence of ⟨K eff ⟩ on T and, correspondingly, to a stable behavior vs temperature of initial permeability and energy loss, from DC to the deep megahertz range. By determining the matrix of ⟨K eff ⟩ (CoO, T) values, we are eventually able to predict the dependence of the quasistatic (hysteresis) energy loss W h on the CoO content at different temperatures and proceed to the analysis of the broadband dynamic loss.…”

“…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.…”

Energy Losses in Soft Magnetic Materials Under Symmetric and Asymmetric Induction Waveforms

“…However, the quantitative assessment of the loss properties over the many-decade frequency range useful for applications reveals a complex task. To simplify the matter, quasi-linear DC constitutive equation is therefore assumed, so that the concept of complex permeability and related energy loss, according to (2), applies [24], [25], [26]. The shape of the actually measured DC hysteresis loops (Bp = 0.1 T), shown Fig.…”

“…The rotational (classical) loss Wrot(Bp, f) is then obtained with (2), after suitable integration over the distribution functions for amplitude and orientation of the anisotropy fields. A detailed discussion on the physical assumptions and the performed calculations, including the possible contribution by eddy currents in sufficiently thick specimens, is given in [24] [26]. Fig.…”