Magnetostrictive properties of amorphous SmCo thin films with imprinted anisotropy

Abstract

We examine the magnetostriction in amorphous SmCo thin films with a composition in the range 4-27 at. % Sm. The magnetostriction increases significantly with increasing Sm content but is small compared to terbium-based ferromagnetic compounds, despite the large imprinted anisotropy. The magnetostriction and anisotropy both increase approximately linearly as the temperature is reduced. The magnetoelastic energy is found to be far smaller than the anisotropy energy so the magnetoelastic atomic displacements during growth cannot be the origin of the imprinted anisotropy. The anisotropy is only slightly altered by the application of large tensile stresses, indicating that the local strain fields involved in magnetostriction are not equivalent to the global strain produced by mechanical bending.

Local structure in amorphous Sm$$_x$$Co$$_{1-x}$$: a combined experimental and theoretical study

“…Finally, a 3nm-thick capping layer of amorphous AlZr was deposited to protect the underlying material from oxidation. Two in situ permanent magnets supplied a magnetic field of approximately 0.10 T parallel to the plane of the film during growth, to imprint an anisotropy axis [3,7]. Actual compositions were determined via Rutherford backscattering spectrometry (RBS) at the Tandem Laboratory, Uppsala, and the thickness and density of each film were determined by X-ray reflectivity (XRR).…”

“…amorphous thin films and heterostructures exhibit highly uniform interfaces [5,6], which is often a desirable property for applications. Recently, several amorphous Sm-Co thin film and heterostructure systems have been investigated [3,[7][8][9], with particular focus on their magnetic properties. These amorphous Sm-Co alloys retain much of the high magnetic moments that their crystalline counterparts are known for [10], but with a greatly reduced coercivity [3] and high degree of tunability due to a wide range of available compositions.…”

Multi-phase field modeling and simulation of magnetically driven grain boundary migration in SmCo polycrystals

“…Depending on the material class, for example, the giant magnetostrictive materials [35], the magnetostriction may have an impact on the grain evolution and can be added in the same formalism. However, for the test case of SmCo, the magnetostriction coefficient is small [36] and the anisotropy is probably more relevant.…”

Finding order in disorder: Magnetic coupling distributions and competing anisotropies in an amorphous metal alloy

“…These are essentially superparamagnetic regions that are easily polarizable and can mediate exchange coupling and proximity effects over several tens of nanometers. 24,27 As shown in Fig. 3, there is a strong change in effective coupling strength with composition in CoAlZr, meaning that there can potentially be a large variation in the local Curie temperature within each sample.…”

“…During growth, we apply a uniform magnetic field parallel to the film plane that has been shown to induce a uniaxial anisotropy in thin magnetic films, with the easy axis direction parallel to the applied field. 15,19,24,27,28 The hysteresis loop parallel to the growth field is square, with a sharp single switch and a very low coercive field of Hc ≈ 0.2 mT. In the perpendicular inplane direction, the loop has zero remanence but saturates at a low field.…”