Refining single-crystalline epsilon iron oxide nanorods via low-temperature aging

Particle size effect on millimeter-wave absorption, rotation, and ellipticity of gallium-substituted epsilon iron oxide

Various applications employ millimeter waves. For example, the carrier frequencies of vehicle radar in advanced driver assistance systems are 76–81 GHz millimeter waves. Here, we investigate the particle size effect on millimeter-wave absorption of gallium-substituted epsilon iron oxide ε-Ga_xFe_2−xO₃ with x = 0.44 ± 0.01. Samples were composed of nanoparticles with sizes of 16.9(1) nm, 28.8(2) nm, and 41.4(1) nm. Millimeter wave absorption, Faraday rotation, and Faraday ellipticity were measured by terahertz time-domain spectroscopy. This series exhibits millimeter-wave absorption at 78.7, 78.2, and 77.7 GHz without an external magnetic field. The millimeter-wave absorption increases from 4.6 dB to 9.4 dB as the particle size increases. In the magnetized sample, the Faraday rotation angle increases from 9.1° to 18.4°, while the Faraday ellipticity increases from 0.27 to 0.52. The particle size effect can be explained by the change in the ratio of the surface and core of the nanoparticles. The present study should contribute to the realization of high-performance millimeter-wave absorbers.

Increasing the particle size improves the millimeter-wave absorption and rotation properties of gallium-substituted epsilon iron oxide.

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.

A review on the origin of nanofibers/nanorods structures and applications

In this review work, we highlight the origin of morphological structures such as nanofibers/nanorods in case of various materials in nano as well as bulk form. In addition, a discussion on different cations of different ionic radii and other intrinsic factors is provided. The materials (ceramic titanates, ferrites, hexaferrites, oxides, organic/inorganic composites, etc.,) exhibiting the nanofibers/nanorods like morphological structures are tabulated. Furthermore, the significance of nanofibers/nanorods obtained from distinct materials is elucidated in multiple scientific and technological fields. At the end, the device applications of these morphological species are also described in the current technology. The nucleation and growth mechanism of α-MnO₂ nanorods using natural extracts from Malus domestica and Vitis vinifera [3].