Synthesis of a High-Coercivity FePt–Ag Nanocomposite Magnet via Block Copolymer-Templated Self-Assembly

Received Jun 30, 2017; Revised Sep 28, 2017; Accepted Oct 30, 2017

This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1. Introduction

Along with recent improvements in the processing capability of computers, the capacity of the hard disk drive as an external storage device has also dramatically increased. Magnetic recording media are rapidly becoming popular not only for personal computers but also for consumer electronics such as video recorders, and demand for such media will likely increase as high-resolution digital television broadcasting becomes more common. In addition, as the IoT develops, further data densification will be required so that digital data can be recorded for longer periods of time and so that the portability of related equipment using magnetic recording media can be increased by means of miniaturization.

Magnetic recording media are composed of magnetic thin films consisting of magnetically isolated crystallites [1–6]. Increasing the recording density requires a reduction in the medium area for a single bit, which in turn necessitates a proportional decrease in the volume of the magnetic particles constituting the medium. However, decreasing the particle volume results in deterioration of resistance to thermal disturbance and in magnetization reversal due to thermal fluctuation, and consequently information cannot be recorded on the medium [7–9].

The thermal fluctuation problem can be minimized by using magnetic recording media with a high magnetic anisotropy (Ku) [10, 11]. The ordered L1₀ FePt phase has Ku of at least 10 times that of the currently used CoCr alloy system [12], and this material is the most promising candidate for a high-Ku medium. However, for practical use of L1₀ ordered alloys as recording media, it will be necessary to realize high coercivity by fabricating nanocrystalline grains, controlling (001) orientation, and forming grain boundaries with the nonmagnetic phase [10, 13].

Sputtering is the most commonly used method for fabricating FePt nanostructures [14–18], but this method, which requires high vacuum and high energy, is too...