Prof. Shien-Uang Jen
Institute of Physics, Academia Sinica, Chinese Taipei
Title: Field annealing effect on magnetostriction and sensitivity of the ferromagnetic Fe60Co18Ga22/Si(100) film
Abstract:
The field anneal (FA) method is a very common technique used to define an easy axis (EA) in a ferromagnetic material. The pair-ordering mechanism, biased by the annealing field (h), can cause a local structure, which tends to align the saturation magnetization (MS) or magnetic domain orientation. Nevertheless, there may exist a second (or different) FA mechanism, which is important in the application of magnetostrictive materials. Namely, in Ref. [1] it was mentioned that for the Fe-Ga (Galfenol) alloys the abnormally large magnetostriction can be associated with the magnetic field-induced flip of tetragonal axes of the ordered (L12) phase crystals in the A2 + D03 matrix.
In this study, as-deposit (AD) and field-anneal (FA) Fe60Co18Ga22 films have been made. We found that after FA treatment, both the macro-stress and saturation magnetostriction in the film increase greatly. Also, after FA treatment, the tetragonal L12 phase shows up, and coexists within the original two-phase (A2 + D03) field. In agreement with the theory, the occurrence of large stress and magnetostriction is related to the magnetic-field-induced flip of the tetragonal axis of the L12 phase crystal by FA. As a low-field sensor, FA could enhance the sensitivity of the Fe60Co18Ga22 film element up to 18.9 ppm/Oe.
[1] J. Boisse, H. Zapolsky, A.G. Khachaturyan, Acta Mater. 59 (2011) 2656 – 2668.
Biography:
My name is Shien-Uang Jen. Currently, I am a senior Research Fellow at the Institute of Physics, Academia Sinica, Taiwan, and a Professor at the Department of Mechanical Engineering, National Taiwan University of Science and Technology.
I received my BS degree from the Physics Department of National Taiwan University in 1976, and my PhD from the Physics Department of Carnegie-Mellon University (USA) in 19863. My research interests are related to Physics of Magnetism: including the electron transport, magnetic, magneto-elastic, magnetic domain and magnetic resonance properties of ferromagnetic materials. In the last 30 years. I have advised over 150 (PhD or MS) students to work on their Theses, respectively. Up to now, we have published about 135 papers in SCI journals. I also hold one US patent and one TW patent. In 2012 I received an invention award from National Science Council, and in 2016 a reviewer recognition award from Elsevier.