Magnetické vlastnosti partikulárních látek na bázi magnetitu.

Abstract

The topic of the dissertation are magnetic qualities of particle substances on the basis of magnetite. Systems which are rich in iron, studied in terms of magnetic effects on biological systems (magnetoreception, biosensorics, etc.), are a modern area of nanotechnologies. The mentioned magnetic properties are investigated in this thesis by a process of constructing Henkel plots obtained from the measurement of virgin and hysteresis loops using vibrational sample magnetometer VSM EV9 from Microsense. The examined material comprises mixtures consisting of magnetite (of the size of 50 - 100 nm) blended with diamagnetic matrix of magnesium oxide (of the sizes of ≈ 9 μm, ≈ 260 nm and ≈ 2 μm). The dissertation focuses predominantly on the study of interparticle magnetic interactions of the mentioned mixed samples, both depending on the size of the particles of the individually used components and on the selected means of sample preparation. The aim of this work is the understanding of magnetic interaction mechanism in the presented nanoparticle mixtures. The criterion is the evaluation of the influence of the preparation technology of the individual samples, the influence of the proportional composition of the individual mixture components and the effect of the particle size of diamagnetic mixture component depending on the intensity of the interparticle magnetic interactions. The results include among others pictures from x-ray dispersion analysis and scanning electronic microscope for the selected samples. It was found out that the ratio of magnetic and non-magnetic components and the temperature influences the intensity of the mentioned interactions. For system Fe3O4 /MgO (≈ 9 μm), a suitable magnetic ratio appears to be 30 weight % of magnetite, since the interactions are the most intensive with this concentration. Possible reasons of such effect are discussed in the thesis.