Magnetic, magneto-elastic, and magnetic domain properties of Galfenol films


Prof. S. U. Jen

Institute of Physics, Academia Sinica, Taipei, Taiwan

Data 03.07.2017 

ap. B-607

11-00 a.m.

Abstract:

 

In my talk, I shall briefly discuss how we did the following measurements and the analyzing work on the Galfenol films: [1] the magnetostriction measurement by using an integrated digital holographic microscopy (DHM) system with an in-plane external field up to 2 KOe1 ; [2] the intrinsic stress measurement by using the laser scan of the film surface2; and [3] the magnetic domain images obtained by using an integrated magnetic force microscope (MFM) with an in-plane field up to 150 Oe2. The so-called Galfenol films were made by the magnetron sputtering technique with a rotation of the substrate and at room temperature: they are the Fe81Ga19/Si(100), Fe81-XGaXGa19/Si(100), and Fe81-XGaXGa19/glass films, with x or y = 0 – 23 at%Ga.  First, I am going to show the visual magnetostriction effect of the Galfenol films: i.e., the 3D and/or 2D deflection contours of the film surface under the longitudinal field (Hǁ) or the transverse field (H). From the curvature measurements of the bent surfaces, we could determine the saturated longitudinal magnetostriction (l) and transverse magnetostriction (lS). Then, it is easy to find the saturation magnetostriction (lS).  The trends for the x and y dependence of lS are the same: i.e., when x = y = 19 at.%Ga, lS reaches the maximum value, lS = 92 and 70ppm, respectively.  Second, from the stress measurements, we found that the intrinsic stresses in the Fe81Ga19 film are biaxial and compressive: i.e., sxx = -420 MPa and syy = -656 MPa.  Third, from the magneto-elastic calculations, the Galfenol films should exhibit an in-plane uniaxial anisotropy, which agrees with the observations from the squareness vs. rotation angle plot: two-fold symmetry with an 180o period and easy axis parallel to sxx.  Finally, the domain patterns at each chosen point on the easy-axis magnetic hysteresis loop are revealed for analysis.

 

1.S. U. Jen, C. C. Liu, and S. T. Chen, IEEE Trans. MAG-50, 6000404(2014).

2.S. U. Jen and C. C. Liu, J. Appl. Phys.115, 013909(2014).

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