Underlayer effect on the soft magnetic, high frequency, and magnetostrictive properties of FeGa thin films

Abstract

The soft magnetic, microstructural, and magnetostrictive properties of Fe81Ga19 (FeGa) film sputter deposited onto 2.5-nm Ta, Cu, and Ni80Fe20 (NiFe) underlayers were investigated. The films deposited with an underlayer showed increased in-plane uniaxial anisotropy and a decrease in in-plane coercivity. The smallest coercivity was observed in FeGa deposited with a NiFe underlayer at 15 Oe, compared to 84 Oe for films deposited directly on Si. In addition, an effective Gilbert damping coefficient (αeff) as low as 0.044 was achieved for a 100-nm FeGa film with a NiFe underlayer. The coercivity and αeff were shown to decrease further as a function of FeGa film thickness. The FeGa films were also able to retain or increase their saturation magnetostriction when deposited on an underlayer. This enhancement is attributable to the impact of the underlayer to promote an increased (110) film texture and smaller grain size, which is correlated to the lattice match of the underlayer of the sputtered FeGa film. Among the underlayers studied, NiFe promoted the best enhancement in the soft magnetic properties for FeGa thin films, making it an attractive material for both strain-mediated magnetoelectric and microwave device applications.

Magnetic state switching in FeGa microstructures

“…The orientation of the cubic nano-crystallite axes (e.g., <100>, <110>, and <111>) are impacted by the dominant grain orientation from the growth process. For instance, sputterdeposited FeGa films with columnar growth reported in the literature were textured films with a (110) out-of-plane (OOP) crystallographic orientation as shown in Figure 4 (d) with an average column diameter (i.e., Grain Size, GS) of ~40 nm [13]. The zoom-in image of Figure 4 (d) shows the easy axes orientations [100] and [010] at 45º from the OOP direction, and the [001] in the in-plane orientation (out of page).…”

“…The substrate was poled by applying an electric field of 0.8 MV m −1 through the thickness of the substrate prior to deposition. The FeGa layer was deposited on the grounded side of the substrate using a ULVAC JSP-8000 DC magnetron sputtering system with a base pressure of 2 × 10 -7 Torr, DC sputtering power of 200 W, Ar working pressure of 0.5 mTorr and an FeGa target with atomic ratio of 85:15 for elements Fe and Ga. Is believed that these films are textured, since sputtered deposited FeGa is known to grow as columnar grains [13]. Tantalum films were deposited on both sides of the FeGa film as barrier and capping layers.…”

“…FeGa is cost effective, oxidation resistant, machinable, and has advantageous mechanical properties [12]. Several groups have deposited high quality FeGa textured thin films using DC magnetron sputtering [12][13][14]. Switching mechanisms in FeGa nanoscale heterostructures have been explored for memory [15] and dipole-dipole coupled logic devices [16].…”

Magnetic Properties Regulation of FeGa and FeGaNi Films with Oblique Magnetron Sputtering

“…To achieve a good high frequency permeability, the material should possess low coercivity (H c ) and a high remanence ratio (M r /M s ), which is used in high-frequency applications [11,12]. The FeGa/Magnetic heterostructures such as FeGa/FeNi [18], FeGa/Mn [19], Fe 75.5 Cu 1 Nb 3 Si 13.5 B 7 /FeGa [20], FeGa/Cu [21], FeGa/Ta [22], FeGa/diamond [23], and FeGa/ZnSe [11] were used to improve the soft magnetic properties through the interfacial interaction, the number of layers, and their thicknesses. For the heterostructure of hard and soft ferromagnets in films, a strong exchange spring magnetism assumes the responsibility of explaining the enhanced static and dynamic magnetic properties.…”