Development of a magnetic recording tape using epsilon iron oxide - School of Science, the University of Tokyo
Sep 5, 2016

Development of a magnetic recording tape using epsilon iron oxide

-Observation of sharp regenerative signal with low noise-

 

Shin-ichi Ohkoshi
 (Department of Chemistry, School of Science, The University of Tokyo, Professor)
Asuka Namai
 (Department of Chemistry, School of Science, The University of Tokyo, Assistant Professor)

 

Main points of the press release

  • Based on epsilon iron oxide (ε-Fe2O3), a new series of nanomagnet was developed for next-generation magnetic tape, by substituting the Fe ion with several metal ions.
  • A magnetic tape was developed by using this nanomagnet. The developed magnetic tape showed an extremely low media noise and a very sharp signal, which is required for next-generation magnetic tape.
  • The demand for magnetic tapes as large capacity archive recording media is rapidly growing in the big-data era with explosive increase in the information to be recorded. The present research result is expected to contribute to this social demand.

Overview of the press release

A research group of Prof. Shin-ichi Ohkoshi et al. at the University of Tokyo developed a new series of nanomagnet based on epsilon iron oxide (ε-Fe2O3 )[1], ε-Ga0.31Ti0.05Co0.05Fe1.59O3, where Fe ions of ε-Fe2O3 are substituted by three metal ions, i.e., gallium ion, titanium ion, and cobalt ion (hereafter called GTC-type epsilon iron oxide). By controlling the metal substitution ratios, the coercive field [2]of this GTC-type epsilon iron oxide was tuned to a suitable value for magnetic recording of 3 kilo-oersted (kOe). The magnetization value also improved from ε-Fe2O3 by 44%. GTC-type epsilon iron oxide nanomagnet was then synthesized in a medium-size production scale (5 kg), and a trial production of a magnetic tape was developed. The regenerative signal of the manufactured magnetic tape was very sharp, and the media noise was found to be extremely low. Therefore, GTC-type epsilon iron oxide nanomagnet is expected as next-generation magnetic recording material for magnetic tapes in large capacity archiving.

The present research result will be released online as a Hot Paper from the journal of the German Chemical Society, Angewandte Chemie International Edition, on August 24, 2016 (WED) at 7 p.m. Japan standard time.

Contents of the press release

Among the various recording media such as hard disc drives, magnetic tapes are presently attracting much attention with increasing market demands. This trend is even expressed as “revival” of magnetic tapes. We are now rushing into the big-data era with explosive increase of information, and the role of recording media for archiving is expanding. Especially, magnetic tapes are actively used in many places such as insurance companies, banks, broadcasters, and web services such as Google and Facebook, for their long-term guarantee and low cost. As magnetic particles for magnetic tapes, metal powders (cobalt-iron nanoparticles) have long been used. Recently, due to technological innovation by magnetic tape manufacturers, development of magnetic tapes for high-density recording is being actively carried out, e.g., the development of the recent product using barium ferrite. Investigation of new materials for next-generation magnetic tapes is also on the move, and a new magnetic ferrite of epsilon iron oxide (ε-Fe2O3), the world smallest hard ferrite [3], is drawing attention as a strong candidate.

In the present work, Prof. Ohkoshi et al. chemically synthesize ε-Ga0.31Ti0.05Co0.05Fe1.59O3 (GTC-type epsilon iron oxide) nanomagnet, where the Fe ion of ε-Fe2O3 is substituted with gallium ion (Ga3+), titanium ion (Ti4+), and cobalt ion (Co2+) (Figure 1).

Figure 1. (a) Crystal structure, (b) photograph of the large-scale produced powder sample (a portion), and (c) magnetic hysteresis curve at room temperature of GTC-type epsilon iron oxide magnetic nanoparticles. Inset is the transmission electron microscopy image.

 

In this series of GTC-type epsilon iron oxide, the coercive field of 3 kilo-oersted (kOe), which is the suitable value for magnetic recording, was achieved by tuning the metal substitution ratios. The magnetization value was also improved from ε-Fe2O3 by 44%, showing that this material exhibits the suitable performance for magnetic recording. GTC-type epsilon iron oxide was synthesized in a medium-size production scale (5 kg), and a trial production of a magnetic tape was developed (Figure 2).

Figure 2. (a) Photograph, (b) schematic illustration of the magnetic tape structure, and (c) cross section scanning electron microscopy image of the manufactured magnetic tape. (d) Regenerated signal of the manufactured GTC-type epsilon iron oxide magnetic tape and the conventional cobalt-iron nanoparticle (MP1, for reference) tape. Comparing the signals of the present material (red line) and that of cobalt-iron nanoparticle tape (gray line), the media noise is very low and is suppressed to about 1/10. The signal waveform is very sharp, and therefore, the magnetic tape composed of GTC-type epsilon iron oxide was found to possess high performances.

 

This magnetic tape is composed of a magnetic recording layer of GTC-type epsilon iron oxide and a nonmagnetic layer on a base film with a back coat covering the bottom of the tape. The regenerative signal of the manufactured magnetic tape was very sharp and the media noise was suppressed to about 1/10, compared to the conventional tape using metal powder (cobalt-iron nanoparticles, MP1) (Figure 2d), indicating that the present material possesses significant properties demanded for next-generation magnetic tapes.

In the present series of GTC-type epsilon iron oxide, the magnetic properties was tuned into the demanded spec for magnetic recording, and the magnetic tape using this material was found to exhibit significant performance. GTC-type epsilon iron oxide is expected as next-generation magnetic recording material for archiving large amount of data with high-density.

 

Publication journal

Journal

Angewandte Chemie International Edition

(journal of the German Chemical Society), Early View article (highlighted as “Hot Paper”)

Title Multimetal-Substituted Epsilon-Iron Oxide ε-Ga0.31Ti0.05Co0.05Fe1.59O3 for Next Generation Magnetic Recording Tape in the Big-Data Era
Authors Shin-ichi Ohkoshi,* Asuka Namai, Marie Yoshikiyo, Kenta Imoto, Kazunori Tamazaki, Koji Matsuno, Osamu Inoue, Tsutomu Ide, Kenji Masada, Masahiro Goto, Takashi Goto, Takayuki Yoshida, and Tatsuro Miyazaki
DOI No 10.1038/srep27212
Abstract URL

 

Contact information

Scientific
 Department of Chemistry, School of Science, The University of Tokyo
 Professor Shin-ichi Ohkoshi

 E-mail:ohkoshi[@]chem.s.u-tokyo.ac.jp

 

Glossary

[1] Epsilon iron oxide (ε-Fe2O3)

Prof. Shin-ichi Ohkoshi et al. firstly reported pure epsilon iron oxide (ε-Fe2O3) in 2004, by utilizing nanoparticle synthesis methods. They revealed that ε-Fe2O3 exhibits the largest coercive field over 20 kilo-oersted (kOe) among ferrite magnets. They have also reported that ε-Fe2O3 is the world smallest hard ferrite magnet and that it shows high frequency millimeter wave absorption. ε-Fe2O3 and metal-substituted ε-Fe2O3 is expected to be applied to next-generation magnetic recording media for large capacity data storage and millimeter wave absorbing material for automobile driving support systems, etc. Therefore, this material is drawing attention as a new material contributing to the future society represented by big data and IoT (Internet of Things). ε-Fe2O3 powder and paint samples are displayed in the special exhibition at Science Museum, London from July 15, 2016.

[2] Coercive field (Hc)

The strength of external magnetic field that is necessary to flip the magnetization of a magnet that is magnetized toward a particular direction.

[3] World smallest hard ferrite

ε-Fe2O3 maintains its properties as a magnet down to a very small size of 7.5 nanometers (nm, thousand millionth of a meter) [S. Ohkoshi, et al., Scientific Reports, 5, 14414 (2015)]. To achieve high-density magnetic recording media, it is necessary to downsize the magnetic particles. The smallest hard ferrite, ε-Fe2O3, is introduced in the roadmap of magnetic tape industry.

― Office of Communication ―

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