Thickness dependence of magnetization reversal and magnetostriction in Fe81Ga19 thin films

Abstract

Among the magnetostrictive alloys the one formed of iron and gallium (called "Galfenol" from its U.S. Office of Naval Research discoverers in the late 90's) is attractive for its low hysteresis, good tensile stress, good machinability and its rare-earth free composition. One of its applications is its association with a piezoelectric material to form a extrinsic multiferroic composite as an alternative to the rare room temperature intrinsic multiferroics such as BiFeO 3 . This study focuses on thin Fe 0.81 Ga 0.19 films of thickness 5, 10, 20 and 60 nm deposited by sputtering onto glass substrates. Magnetization reversal study reveals a well-defined symmetry with two principal directions independent of the thickness. The magnetic signature of this magnetic anisotropy decreases with increasing FeGa thickness due to an increase of the non-preferential polycrystalline arrangement, as revealed by transmission electron microscopy (TEM) observations. Thus when magnetic field is applied along these specific directions, magnetization reversal is mainly coherent for the thinnest sample as seen from the transverse magnetization cycles. Magnetostriction coefficient reaches 20 ppm for the 5 nm film and decreases for thicker samples, where polycrystalline part with non-preferential orientation prevails.PACS numbers: 68.55.-a, 68.35.bd,75.60.-d, 75.75.-c,75.80.+q, 81.15.Cd Keywords: Magnetization reversal, magnetic thin films. Thermoelasticity and electromagnetic elasticity (electroelasticity, magnetoelasticity). Beam, plate, and shell. Magnetic properties of monolayers and thin films. Magnetomechanical and magnetoelectric effect, magnetostriction. arXiv:1903.05397v2 [cond-mat.mtrl-sci]

Unveiling the Different Physical Origins of Magnetic Anisotropy and Magnetoelasticity in Ga-Rich FeGa Thin Films

“…However, no significant variation for B 1 and B 2 with respect to the bulk values has been reported for FeGa epitaxial films 15 . On the other hand, because B eff can be expressed in terms of the crystallite axis distribution, changes of the values of the magnetostriction can be related to variations in the crystal texture of the films 36 . This consideration can be applied straightforward to the films studied here since deviations from the random distribution for the in-plane crystallite direction can result in the weakening of |<B eff >|.…”

Ultralow magnetostrictive flexible ferromagnetic nanowires

“…35 The fitting procedure was limited to the practical elastic regime of the sample, i.e., up to 2 GPa of external stress. Note that the film thickness is within the range for efficient stress transfer, 36,37 and we did not notice any physical change or thin films to be detached from the substrates during or after the experiments. Beyond physical observations, the most sensitive way to detect permanent plastic deformation is offered by the magnetoelastic behavior itself, where we see a marked deviation from the expected linear elastic regime, only for 3 GPa of external stress.…”

“…Additional contributions to the deviation with respect to bulk can emerge from the eventual strain at the substrate interface, 45 the surface roughness of the system, 49 and possible crystalline structural reorganization in the thin layer. 36 This implies that the further reduction of the effective magnetostriction to the reduced dimensionality of the NWs from 2D to 1D geometry is due to enhanced S/V and the enhanced local topological modifications and nanostructured interfaces, making the surface magnetostriction properties dominant over the bulk behavior. For each step of reduced dimensionality (bulk → film → NWs), nearly one order reduction in the magnitude of λ σ has been observed.…”

Twisting and Reverse Magnetic Field Effects on Energy Conversion of Magnetostrictive Wire Metal Matrix Composites

“…[ 1–3 ] There are a series of imminent challenges that not only solve the power supplies with long‐lasting lifetime and miniaturization but also improve the performance of sensors and actuators with sufficient energy conversion, signal transmission, and stability. [ 4,5 ] The magnetostrictive materials that have been widely studied over the last decades offer a promising alternative for solving these problems. Following the development and improvement in processing technique and composition change, many magnetostrictive materials including their composites with excellent magnetostrictive properties have been successfully fabricated, which provides expecting feasibility for these materials that were used in smart detective components and self‐powered microsystems.…”