Alternative Current Magnetic Permeability of Fe 81 Ga 19 Alloy with Bias Magnetic Fields
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Alternative Current Magnetic Permeability of Fe81Ga19 Alloy with Bias Magnetic Fields Hongping Zhang1, Guangheng Wu2, Zheng Liu3, Lihong Xu1, Lei Wang1, Zhaofu Du1, Yongmao Pei4 and Dongliang Zhao1 1
Central Iron and Steel Research Institute, Beijing 100081, China
2
Institute of Physics, Chinese Academy of Sciences, Beijing 10080, China
3
National Library of ChinaˈBeijing 100081, China
4
Beijing Institute of Technology, Beijing 100081, China
ABSTRACT In this study, the AC magnetic permeability of polycrystalline Fe81Ga19 alloy (Galfenol), without crystal orientation under both the bias applied fields and frequencies, was investigated by the method of measuring inductance of ring specimens. The results showed that the AC permeability of the alloy can reach more than 160 Gs/Oe under the conditions of low frequencies or quasi-static state. The permeability decreased with the increase of frequency. When the frequency was higher than 6 kHz, the permeability decreased slowly, and gradually stabilized with the increase of frequency. When applying a little of parallel bias magnetic field, the permeability decreases obviously with the increase of frequency. But applying a perpendicular bias magnetic fields, the permeability of the only initial point of the measuring frequency decreases a little compared to the permeability without bias field. INTRODUCTION As reported in the previous works, the magnetic anisotropy of Fe will change and magnetostriction of Fe will enhance if the nonmagnetic elements V, Cr and Al are added to bcc Fe [1]. When the nonmagnetic element Ga is added to bcc Fe, the magnetostriction of Fe will enhance ten times [2]. It has been proven that a content of 19 at. % Ga is an optimized composition for the magnetostriction in Fe-Ga single crystals. This composition gives the material a saturation magnetization field of about several hundred Oe, and it also gives the material a saturation magnetostriction larger than 300 ppm [3-5]. Although the magnetostriction values of Fe-Ga alloys are only 1/5~1/8 the values of Tb-Dy-Fe alloys (Terfenol-D), the mechanical properties and ductility of Fe-Ga alloys are better than that of Tb-Dy-Fe alloys. The tensile strength of Fe-Ga alloys are higher than 440 MPa [6], which is much larger than that of Tb-Dy-Fe alloys (25 MPa). Besides the magnetostriction properties, the magnetic permeability of the active materials is another important parameter in the design of the magnetizing fields of
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the magnetostrictive transducer, especially the alternative current permeability under an external bias magnetic field. Since the magnetostrictive materials have a nonlinear feature, the permeability is not constant if the external physical environment changes. The properties of the permeability will determine the designs of the magnetization fields in applied devices. In this study, the AC magnetic permeability of the bcc Fe81Ga19 magnetostrictive alloy was investigated under both bias magnetic fields and AC frequencies. EXPERIMENT AND METHODS In the previous works, rod samp
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