First‐Principles Calculations and Optical Absorption Spectrum of a Light‐Colored Aluminum‐Substituted ε‐Iron Oxide Magnet

• Published in: European journal of inorganic chemistry Vol. 2017; no. 3; pp. 531 - 534
• Main Authors: Nasu, Tomomichi, Yoshikiyo, Marie, Tokoro, Hiroko, Namai, Asuka, Ohkoshi, Shin‐ichi
• Format: Journal Article
• Language: English
• Published: 18.01.2017
• Subjects: Absorption; Aluminum; Colors (materials); Electronic structure; Energy gaps (solid state); Iron; Magnetic materials; Magnetic properties; Materials science; Mathematical analysis; Nanoparticles; Periodic structures; Toners
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201601169

In this paper, we report the electronic structure and optical properties of Al‐substituted ε‐Fe2O3. First‐principles calculations of the periodic structure of ε‐Al0.5Fe1.5O3 reveal that the band gaps (Eg) are 2.6 (480 nm) and 2.5 eV (500 nm) for the up‐spin and down‐spin transitions, respectively. To investigate the electronic structure, a highly dispersed polymer solution composed of ε‐Al0.66Fe1.34O3 nanoparticles was prepared. This solution is light orange in color; the absorption coefficients (ε) are small with values of 810 and 260 dm3 mol–1 cm–1 at 3.1 (400 nm) and 2.6 eV (480 nm), respectively. The reason why Al‐substituted ε‐Fe2O3 is so light in color can be understood by the disappearance of the energy states in the conduction and valence bands, which originates from the tetrahedral D site. Such a light‐colored magnetic material should be useful for colored magnetic toners for color printing. Periodic structure calculations of Al‐substituted ε‐Fe2O3 reveal that ε‐Al0.5Fe1.5O3 has a wide band gap. A highly dispersed polymer solution of the ε‐Al0.66Fe1.34O3 nanomagnet is prepared, and it is very light in color relative to other magnetic ferrites. Such a light‐colored magnetic material should be useful for colored magnetic toners for color printing.