Design of modern magnetic materials with giant coercivity

The review is devoted to compounds and materials demonstrating extremely high magnetic hardness. The recent advances in the synthesis of modern materials for permanent magnets are considered, and a range of exotic compounds interesting for fundamental research is described. The key details of chemical composition, crystal structure and magnetic microstructure responsible for the appearance of high magnetic anisotropy and giant coercivity are analyzed. The challenges of developing the title materials are noted and strategies for their solution are discussed.

The bibliography includes 389 references.

Advances in magnetic films of epsilon-iron oxide toward next-generation high-density recording media

Iron oxide magnets, which are composed of the common elements iron and oxygen, are called ferrite magnets. They have diverse applications because they are chemically stable and inexpensive. Epsilon-iron oxide (ε-Fe2O3) is a polymorph that shows an extremely large coercive field as a magnetic oxide. It maintains its ferromagnetic ordering even when downsized to a single nano-sized scale (i.e.,<10 nm). Due to these characteristics, ε-Fe2O3 is highly expected to be used for high-density magnetic recording media in the big data era. Here, we describe the recent developments of magnetic films composed of metal-substituted ε-iron oxide, ε-MxFe2-xO3 (M: substitution metal), toward the next-generation of magnetic media.

Three-Dimensional Microstructure of ε-Fe2O3 Crystals in Ancient Chinese Sauce Glaze Porcelain Revealed by Focused Ion Beam Scanning Electron Microscopy

Ancient Chinese sauce glaze porcelain has recently received growing attention for the discovery of epsilon iron oxide (ε-Fe₂O₃) crystals in glaze. In this work, we first confirm the presence of ε-Fe₂O₃ microcrystals, in large quantiteis, in sauce glaze porcelain fired at the Qilizhen kiln in Jiangxi province during the Southern Song dynasty. We then employed focused ion beam scanning electron microscopy (FIB-SEM) to investigate the three-dimensional microstructure of ε-Fe₂O₃ microcrystals, which revealed three well-separated layers (labeled, respectively, as LY1, LY2, and LY3 from the glaze surface to inside) under the glaze surface. Specifically, LY1 consists of well-defined dendritic fractal structure with high ordered branches at micrometers scale, LY2 has spherical or irregular-shaped particles at nanometers scale, while LY3 consists of dendrites with four, six, or eight primary branches ranging from several nanometers to around 1 μm. Given these findings, we proposed a process for the possible growth of ε-Fe₂O₃ microcrystals in ancient Chinese sauce glaze.