Tb-Fe及びTb-Fe-Co系薄膜の磁気ひずみ特性

Abstract

We studied Tb-Fe-Co giant magnetostrictive thin films and researched sputtering conditions to improve their magnetostrictive properties and investigated the possibility of their practical use. The sputtering Ar gas pressure influenced their inner stress and played a very important role for the determination of the magnetic easy axis. The largest magnetostriction was obtained when the Ar gas pressure was set at 0.7 Pa and the inner stress was controlled at an about 50 MPa tensile stress. In the Tb-Fe system, the Curie temperature is very low (about 140°C) compared with bulk materials, but the Curie temperature can be improved with increasing Co ratio. For films over 70% Co ratio, the Curie temperature was more than 250°C and the largest magnetostriction 1508 ppm was obtained at 80.1 % Co ratio. At almost all Tb-Fe-Co thin films, the values of magnetostriction were very high (over 1000 ppm), and the coercive forces were low (around 8 kA/m). Therefore, the Tb-Fe-Co giant magnetostrictive thin films are very appropriate materials for the applications in micro actuators and sensors.