| dc.description.abstract | The thesis investigates the effects of the annealing process on the magnetic properties of ferrimagnetic materials. Emphasis is placed on how the magnetic properties might be controlled, through the annealing process, in order to meet the requirements of a particular technical application. The thesis covers the general theory and terminology associated with magnetism in materials and then investigates ferrimagnetism in more detail. Next, some common technical applications of ferrites are outlined and the theory of thermal and magnetic annealing is explained. The thesis concludes with a discussion of the experiments conducted during the project. The objective of the experiments was to see if a soft ferrite could be hardened by thermal annealing, in order to make a better permanent magnet without substantially deteriorating the high permeability or low hysteresis loss of the sample. The results of the experiments revealed that by carefully choosing the cooling rate and monitoring the effects of ambient gas in introducing impurities, a 32% increase in coercive field can be realized over an 18% increase in hysteresis loss, 2.9% decrease in permeability, and a 20% decrease in saturation magnetization. | en |
