Magnetic features of MnZn ferrite for electronic applications

Abstract

MnZn ferrites are one of the most common soft magnetic materials for application in microelectronics as a material for microwave components (transformers, transducers, inductors, magnetic fluids, sensors,). MnZn ferrites attracted attention due to wide range of relative magnetic permeability values (from 103 to 104), high resistivity (consequently low magnetic losses) as well as high thermal stability (high saturation magnetic flux density at high temperatures (Bs > 0.4 T at 100 OC) and a relatively high Curie temperature of about 230 OC).Recently, a variety of technologies have been examined for MnZn ferrite production: powder/ceramic injection moulding (PIM/CIM), chemical co-precipitation method, conventional ceramic processing, sol-gel or microemulsion. In this study a toroidal samples of MnZn ferrites with dimensions appropriate for applications in electronic industry (i.e. microelectronics: inner diameter 3.5 mm, outer diameter 7 mm, height 2 mm) were investigated. Magnetic properties were measured by hysteresis graph (B-H curve at level of magnetic excitation up to 1 kA/m and at different frequencies from 5 Hz to 10 kHz). Relative magnetic permeability as well as magnetic power (active) losses was analyzed as frequency dependent. Very stable maximum magnetic permeability was observed for magnetic field of 200 A/m in the frequency range from 50 Hz (μr ≈ 480) to 10 kHz (μr ≈ 450). Active power referred to unit mass of about 30 W/kg was recorded at frequency of 1 kHz (@ 280 mT). As the hysteresis losses are proportionally to the frequency (~ f) and eddy-current losses are proportionally to the square of frequency (~ f2) it was performed separation between these two components from total magnetic power (active) losses. Numerical fitting of this functionality on frequency were performed and analysed. The results obtained were compared with the catalogue data for other MnZn ferrite components for applications in electronics.