A DC non-contact method for measuring the magnetostrictive strain in thin-films is demonstrated, achieving a state-of-the-art sensitivity of . In this method, an optical profilometer is used to measure the curvature induced in a magnetostrictively coated coverslip under a DC field through phase-sensitive interferometry. From this the magnetostrictive stress and strain are calculated using Stoney’s formula. This addresses limitations of conventional techniques that measure magnetostriction based on the deflection of a cantilever under an AC field, which require complex dedicated set-ups and are sensitive to vibrational noise. Further, it reveals information about the anisotropy of the film and allows for the possibility of measuring multiple samples simultaneously. The theoretical sensitivity limits are derived, predicting a shot-noise-limit of . The method is implemented to measure the magnetostrictive hysteresis and piezomagnetic coupling of thin-film galfenol. Degradation in film performance is observed above a thickness of 206 nm, alongside a change in coercivity. This prompts investigation into the growth and optimization of galfenol films for use in devices.

中文翻译：

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薄膜磁致伸缩的定量轮廓测量

演示了一种用于测量薄膜磁致伸缩应变的直流非接触方法，实现了最先进的灵敏度。在该方法中，光学轮廓仪用于通过相敏干涉测量在直流场下磁致伸缩涂层盖玻片中引起的曲率。由此，使用斯托尼公式计算磁致伸缩应力和应变。这解决了基于交流场下悬臂的偏转来测量磁致伸缩的传统技术的局限性，该技术需要复杂的专用设置并且对振动噪声敏感。此外，它还揭示了有关薄膜各向异性的信息，并允许同时测量多个样品。推导出理论灵敏度极限，预测散粒噪声极限为 。该方法用于测量薄膜加苯酚的磁致伸缩磁滞和压磁耦合。当厚度超过 206 nm 时，观察到薄膜性能下降，同时矫顽力也发生变化。这促使人们对用于设备的加酚薄膜的生长和优化进行研究。