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

Abstract

Effect of (Cu/Fe)O 5 bipyramid size and separation on magnetic and dielectric properties of rare earth layered perovskite LaBaCuFeO 5 and LuBaCuFeO 5

Measuring and modeling broadband magnetic losses versus temperature and aging effects in CoO-doped Mn-Zn ferrites

“…in power electronics), where working temperatures around 100 °C are the rule. It chiefly arises from the smoothing of the dependence of the magnetocrystalline anisotropy <Keff> versus temperature, which we have quantitatively estimated across the whole spectrum of adopted CoO additions [12]. Such estimate, going beyond the usual qualitative assumptions of the literature, follows from the identification of the rotational permeability µrot, as distinguished from the domain wall (DW) permeability µdw.…”

“…It is then possible to qualitatively and quantitatively understand the behavior of magnetic loss and permeability versus frequency under the different conditions and parameters to be faced in applications by separating the DW and rotational contributions to the magnetization process and by correspondingly assessing the behaviors of the loss components. To this end, a specific methodology has been devised, where the measured permeability is decomposed in the rotational µrot = µ'rot -jµ''rot and DW µdw = µ'dw -jµ''dw contributions [12,14]. An example of such decomposition in the 3000 ppm CoO ferrite is shown in Fig.…”

“…where a(Jp) is a parameter lumping the effect of the material microstructure and A is the exchange stiffness constant [12]. Fig.…”

“…The DW permeabilities µ' dw (f) and µ'' dw (f) are obtained by subtracting the rotational quantities from the measured ones. The dashed lines are calculated starting from the Landau-Lifshit z equation for the damped spin precession, as discussed in [12,14]. analytical expression [18] and can be singled out.…”

“…Measurements of the real ρ' and imaginary ρ'' parts of the electrical resistivity, carried out by the four-point method up to 20 MHz, reveal the typical RC response of the Mn-Zn sintered ferrites. ρ' attains a constant value (corresponding to the average resistivity of the grains) and ρ'' becomes negligible, because of the capacitive short provided by the nanometer thick grain boundaries, above about 1 MHz [12].…”