Iron Gallium Magnetostriction Measurement Setup*

Due to the high drive towards improved efficiencies in vibration sensors, there is a search for materials with high magnetostriction. Magnetostriction is the magnetoelastic coupling in response to a rotation of the magnetic moments. An external rotating field will cause the material to deflect at a value proportional to the magnetostriction constant. We built a setup that produces a rotating field to induce uniaxial in-plane stress through two sets of Helmholtz coils while a photonic sensor measures the sample’s deflection. Fe₈₀Ga₂₀samples were prepared by DC magnetron sputtering on Si wafers (250W deposition power, 1.7mTorr, 9.75sccm, Ar flow, 170 nm film thickness).  Samples were sputtered at RT and 300 Celsius. The crystal structure of the thin films was checked with a Rigaku diffractometer. The hysteresis curves of the FeGa samples were measured with a MicroSense Vibrating Sample Magnetometer. The RT sample had a moment density of 1257.56emu/cm³and a coercivity of 17-35 Oe. The sample deposited at 300C had a magnetic density of 866.83emu/cm³and a coercivity of 25 Oe. The result of the magnetostriction measurements on these samples will be discussed.