The composition and magnetic structure of Fe$_{3}$O$_{4}$/$\gamma$-Fe$_{2}$O$_{3}$ core-shell nanocomposites under external magnetic field: Mössbauer study (Part II)

The composition and the magnetic structure of Fe$_{3}$O$_{4}$/$\gamma$-Fe$_{2}$O$_{3}$ nanoparticles placed into external magnetic field with a strength of 1.8 kOe are studied with Mössbauer spectroscopy. We showed that the thickness of the maghemite ($\gamma$-Fe$_{2}$O$_{3}$) shell can be changed by the synthesis conditions. We found that there is a layer, in which the magnetic moments are not oriented collinearly to those located in the depth of the shell, on the surface of maghemite ($\gamma$-Fe$_{2}$O$_{3}$) shell in the Fe$_{3}$O$_{4}$/$\gamma$-Fe$_{2}$O$_{3}$ nanocomposites; in other words, there is a canted spin structure. An intermediate layer in the spin-glass state is formed between the core and the shell. The data on structure of core/shell particles are important to understand the properties of nanocomposites, which are of great interest to apply in various fields, including biomedicine.