TABLE OF CONTENTS The scope of this article is to provide a general introduction to hard magnetic films. It discusses application-relevant extrinsic magnetic properties and focuses on a specific hard magnetic material (Nd 2Fe 14B) to demonstrate the interplay between the film-related microstructure and the magnetic performance. The article by (Kruusing 1999) is a good addendum, as he reviews Nd 2Fe 14B thin films and describes preparation-specific topics.
One area for application of hard magnetic films are microsystem techniques, especially microelectromechanical systems (MEMS). These devices are prepared from relatively thick films (1 5 m) and the high-energy product of the rare earth magnets promises smaller lateral device sizes. Until now, however, only a few systems have been realized, for example a sub-millimeter electric motor (Yamashita et al. 1991), and a stepper motor (Belmans and Hameyer 1998). The challenge facing rare earth magnets in this field is their high corrosion rate when exposing a large surface after structuring. Another potential application is in monolithic microwave integrated circuits (MMICs) (Levy et al. 1996) using thin hard magnetic layers to create bias fields for ferrite devices. Although an optical isolator could be realized this way, this technology has to compete with the conventional technology, which is not based on ferrites.
The largest market for hard magnetic films is in magnetic data storage on computer hard disks. While the bit density increases by about 60% each year, the conventional materials (e.g., CoPtCr, CoCrTa) are expected to reach...
