Magnetite-based glass-ceramics prepared by controlled crystallization of borosilicate glasses: Effect of nucleating agents on magnetic properties and relaxation

Abstract The specific magnetic structure and magnetic relaxation phenomena in magnetite nanoentities grown in a glassy matrix by controlled crystallization of Fe-containing borosilicate and boroaluminosilicate glasses in the presence of two types of nucleating agents, Cr 2 O 3 and P 2 O 5 , were investigated. The structure, morphology and magnetic properties are strongly influenced by the nucleating agents. Cr 2 O 3 generates magnetite-based glass ceramics with magnetite configurations showing an upward relaxation of magnetization at low and high temperatures but downward at intermediate temperatures. The magnetite grown with P 2 O 5 displays only downward relaxation but with different signs of the temperature derivative of the relaxation rate S in different temperature ranges. The observed effects are discussed with respect to the following factors: i ) the existence of a multimodal size distribution of the magnetite (nano)particles as revealed by high resolution electron microscopy; ii ) the degree of occupation of different sublattices of the magnetite structure with Fe 3+ and Fe 2+ ions; and iii ) the interplay between the relaxation mechanisms in different temperature ranges.