Compressive magnetostriction of FeSm alloy film
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1052-DD06-32
Compressive magnetostriction of FeSm alloy film Ryo Nakano1, Yoshihito Matsumura2, and Yoshitake Nishi2 1 Metallurgical Engineering, Graduate School of Engineering, Tokai University, 1117 Kitakaname, Hiratsuka, 259-1292, Japan 2 Science and Technology, Graduate School of Science and Technology, Tokai University, 1117 Kitakaname, Hiratsuka, 259-1292, Japan ABSTRACT The compressive magnetostriction values of Fe2.4Sm alloy thin film prepared on silicon, copper and titanium substrates (300 µm thickness) by direct current magnetron sputtering process were investigated. When the residual gas pressure before argon sputtering and the sputtering pressure of argon gas (5 N) were below 3.2×10-4 Pa and 2.0×10-1 Pa, respectively, the thickness of the Fe2.4Sm films deposited was about 3 µm. Compressive magnetostriction of Fe2.4Sm alloy film deposited on titanium sheet generates large bending motion, compared to those deposited on silicon wafer and copper substrates. High magnetostrictive susceptibility of the films was observed at low magnetic field. INTRODUCTION The RFe2 type cubic Laves phases of rare earth metals (R) and iron (Fe) often show giant magnetostriction [1], which may have applications for sensors and actuators [2,3]. The giant mover strain of Terfenol-D (Tb0.3Dy0.7Fe2), which is larger than that of commercial piezoceramics such as PZT, has been found with low driving potential, high power generation, high responsiveness and wireless operation by a magnetic field [4-8]. In order to create tiny acoustic devices and sensors and actuators driven by low intensity magnetic fields, giant magnetostrictive films have been studied [9,10]. We have reported that a giant magnetostrictive alloy shows a superior characteristic as a thin film actuator. Bending strain in mover devices often depends on substrate thickness. Large motions have been found in mover devices based on of hydrogen storage alloy film on copper thin sheet [11]. In this study, Fe2.4Sm alloy films on silicon, copper and titanium substrates (300 m thickness) have been prepared by a D.C. magnetron sputtering process. The compressive magnetostriction and its susceptibility are evaluated.
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EXPERIMENT The Fe2.4Sm alloy thin film was prepared on a substrate (300 µm thickness) by using D.C. magnetron sputtering. The minimum gas pressure before argon sputtering and the sputtering pressure of argon gas (5 N) were 3.2×10-4 Pa and 0.2 Pa, respectively. The substrate temperature was 423 K (see Table 1). The mean leak rate of the chamber was about 1.96×10-5 Pa m3/s. The sputtering power, deposition time, sputtering distance between target and sheet were 200 W, 3.6 ks and 90 mm, respectively. Mean thickness of the Fe2.4Sm films deposited was about 3 µm. The film composition was analyzed by Energy dispersive X-ray spectroscopy (EDX). Crystalline structures of the prepared film were determined by α-2θ method of thin film X-ray diffraction (Cu-Kα; X’Part-MRD, PHILIPS), where irradiation angle to sample plane was 0.5 deg. The
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