Magnetostriction Measurement of a Ferromagnetic Thin Film Using Digital Holographic Microscope

Magnetostrictive Fe₆₂Co₁₉Ga₁₉ films deposited on Si(100) substrates were used as test samples in this paper: the length (L) is parallel to the x-axis and the width (w) parallel to the y-axis. The conventional magnetostriction measurement includes measuring the free end deflection (Δz) of the cantilevered film-substrate system as a function of the external field (H). In addition, we also used a digital holographic microscope (DHM) to map out the 2-D or 3-D magnetostriction deflection profile, i.e., the deflection, Δz, at any location (x, y) on the film plane, due to H_∥ (the longitudinal field) or H_⊥ (the transverse field). We have compared the saturation magnetostriction (λ_s) data of the test samples, with different w/L ratios, measured by the conventional as well as the DHM method. There are three advantages of the DHM method. First, we could see the deflection motions directly. Second, we could examine the transverse-edge boundary effect on λ_s of the test sample. Third, in agreement with the Saint-Venant´s principle, we could study the effect of clamping on λ_s.