Struktura a studium objemových magnetických vlastností feritových magnetů

Abstract

The goal of this bachelor’s thesis was to examine structure and bulk magnetic properties of five ferrite magnets based on strontium and barium. Magnetic properties were analysed in temperature range from room temperature to 190 °C due to their wide range of technical applications. The results were evaluated based on experimental data measured by X-ray diffraction, scanning electron microscopy with an EDX detector, vibrating sample magnetometer and hysteresigraph. EDX chemical analysis and X-ray diffraction confirmed the SrFe12O19 or BaFe12O19 structure stated by the manufacturer. Based on March parameter evaluated from X-ray diffraction, the magnets were classified into two groups: anisotropic and isotropic ferrites. Anisotropic ferrites showed high particle texturing in the plane (0 0 1). From measurement of bulk J-H a and B-H magnetization curves with increasing temperature were evaluated that both types of ferrites exhibit a linear decrease in remanent flux density, saturation polarization and maximal energy product BHmax. However, the coercive field evaluated from the J-H curve is linearly increasing. Curie temperature evaluated from thermomagnetic curve was around 450 °C for all magnets.