The Composition and Magnetic Structure of Fe<inf>3</inf>O<inf>4</inf>/γ-Fe<inf>2</inf>O<inf>3</inf> Core–Shell Nanocomposites at 300 and 80 K: Mössbauer Study (Part I)

© 2020, Pleiades Publishing, Ltd. Abstract: The magnetic structure and the composition of Fe3O4/γ-Fe2O3 nanoparticles are studied at 300 and 80 K with Mössbauer spectroscopy. We found that the Fe3O4/γ-Fe2O3 particles are a core–shell nanocomposite (NC), in which magnetite Fe3O4 is covered with a maghemite shell (γ-Fe2O3). We showed that the thickness of the maghemite shell (γ-Fe2O3) depends on synthesis technology. We found that a layer, whose magnetic structure differs from that of the inner part of the shell (γ-Fe2O3), is formed on the surface of the maghemite shell (γ-Fe2O3) in the Fe3O4/γ-Fe2O3 NC. An intermediate layer is formed in the spin-glass state between the core and the shell. The data on structure of core–shell nanocomposites open up prospects to explain the properties of such particles, which are of great interest to use in various fields, including biomedicine

The Composition and Magnetic Structure of Fe<inf>3</inf>O<inf>4</inf>/γ-Fe<inf>2</inf>O<inf>3</inf> Core-Shell Nanocomposites under External Magnetic Field: Mössbauer Study (Part II)

© 2020, Pleiades Publishing, Ltd. Abstract: The composition and the magnetic structure of Fe3O4/γ-Fe2O3 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 (γ-Fe2O3) 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 (γ-Fe2O3) shell in the Fe3O4/γ-Fe2O3 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