Abstract
<jats:p>EPR measurements on Fe- and Mn-doped SiCN samples, annealed at various temperatures, revealed that they were superparamagnetic. As well, their EPR spectra depended significantly on the sizes of the nanoparticles. The magnetism of SiCN/Fe is due mainly to the presence of Fe5Si3 and α-Fe superparamagnetic nanoparticles, distributed within the SiCN matrix. On the other hand, the main source of magnetism in SiCN/Mn ceramics is the presence of Mn5Si3Cx and α-Mn nanoparticles. The magnetization measurements on SiCN/Fe reveal that the difference between the ZFC (zero-field cooling) and FC (field cooling) magnetizations decreased with increasing annealing temperatures of the samples, implying that the homogeneity in the distribution of the sizes of nanoparticles increased with increasing annealing temperature. This result can be exploited for practical applications of Fe-doped SiCN nanoceramics as functional materials by annealing these samples at temperatures even higher than 1400 °C. The magnetization and EPR studies of Mn-doped SiCN ceramic indicate the presence of a variety of Mn-containing nanocrystallites, mainly ferromagnetic Mn5Si3Cx nanoparticles. There is also the possibility of presence of ferromagnetic Mn5Si3 nanoparticles with a rather high Curie temperature. The EPR spectra reveal that both Fe- and Mn-doped SiCN nanoparticles exhibit superparamagnetism, or single domain ferromagnetism, depending on their average sizes. They are thus potentially useful in being developed as high-temperature magnetic sensor devices due to SiCN being very stable to temperature variations, and being suitable functional materials for applications to electronics, spintronics and tunable soft magnetics for MEMS/NEMS (micro/nanoelectromechanical systems) devices, requiring homogeneous and uniform material.</jats:p>