Giant Coercive Field of Nanometer‐ Sized Iron Oxide

Abstract

Nanocrystals of iron oxide in a silica matrix exhibiting a giant Hc value of 2.0 T at room temperature are reported. The nanocomposite was obtained by combining reverse‐micelle and sol–gel methods. The nanocrystals of iron oxide are composed of the ϵ‐Fe2O3 phase, with rod‐like particles 100–140 nm long and 20–40 nm wide. The Figure shows the hysteresis curve of the nanocrystals.

Porous Flower-like α-Fe2O3 Nanostructure: A High Performance Anode Material for Lithium-ion Batteries

“…Smaller particle size means shorter path length for diffusion of Li + lithium ion and electronic transport. Recently, the use of nanostructured α-Fe 2 O 3 as an anode material has attracted interest [24], which is largely promoted by the synthesis of diverse α-Fe 2 O 3 nanostructures, including nanoparticles [25], nanocubes [26] nanorods [27], nanotubes [28], and nanoflowers [29] by various routes.…”

Unusual Temperature Dependence of Zero-Field Ferromagnetic Resonance in Millimeter Wave Region on Al-Substituted ε-Fe2O3

“…ε-Fe2O3 had only been known as impurity in iron oxide materials, and its properties were clarified for the first time after our success in the synthesis of single-phase ε-Fe2O3 in 2004 [8].…”

“…Single-phase ε-Fe2O3 nanoparticles are synthesized by a chemical method, combining reversemicelle and sol-gel techniques ( Figure 1) [8][9][10]16]. In the reverse-micelle step, two reversemicelle systems, A and B, are formed by cetyl trimethyl ammonium bromide (CTAB) and 1-butanol in n-octane.…”

“…However, our research group first succeeded in preparing a pure phase of ε-Fe2O3, which is a rare phase of iron oxide Fe2O3 that is scarcely found in nature [8][9][10]. Since then, its physical properties have been actively studied, and one of the representative properties is the gigantic coercive field (Hc) of 20 kilo-oersted (kOe) at room temperature [11][12][13][14][15][16][17][18].…”

High-frequency Millimeter Wave Absorber Composed of a New Series of Iron Oxide Nanomagnets

“…In recent years, we firstly succeeded to obtain a single phase of ε-Fe 2 O 3 nanomagnet (Figure 1), and found that ε-Fe 2 O 3 nanomagnet exhibited an extremely large H c value of 20 kOe at room temperature, which is the highest H c value for insulating magnetic materials. [10][11][12][13][14][15][16][17][18][19] In this paper, we report a new millimeter wave absorber composed of ε-Ga x Fe 2-x O 3 (0.10 ≤ x ≤ 0.67) nanomagnets, which shows a natural resonance in the range of 35-147 GHz at room temperature. 20 This is the first example of a magnetic material which shows a natural resonance above 80 GHz.…”