Giant magnetostrictive materials: thin film formation and application to magnetic surface acoustic wave devices

Abstract

This paper points out current problems in the research and development of giant magnetostrictive materials (GMMs), and the use of thin film GMMs instead of bulk is emphasized because of the ready and inexpensive production and high applicability. One of the most prominent applications using GMM films is the magnetic surface acoustic wave device with tunability under an external magnetic field. Thin films of the giant magnetostrictive Tb 0.3Dy 0.7Fe 2 alloy were prepared by vacuum flash evaporation. The film structure was able to be changed from amorphous to crystalline by controlling the substrate temperature and deposition rate. The crystalline films exhibited much higher magnetization and larger magnetostrictions than did the amorphous films. The contamination of the films in vacuum facilitated amorphization and markedly reduced the magnetostrictions of the films. X-ray diffraction and Auger electron spectroscopy analyses revealed that the ratio of vacuum to deposition rate is an appropriate indicator to assess the contamination effect of films.