Interface induced uniaxial magnetic anisotropy and modified domain patterns in crosslinked silica aerogel/Ni80Fe20 heterostructures

Abstract

Silica aerogels have emerged as promising candidates as platforms for a variety of devices, including those used for magnetic logic and sensing. However, their non-planar structure also poses challenges for their use as substrates for thin film devices. For example, substrate disorder is established to strongly influence anisotropy in thin film magnetic materials. Here, we evaluate the substrate effect on induced uniaxial anisotropy in permalloy (Py) thin films and patterned structures, wherein the uniaxial anisotropy is clearly linked to a directionality of the magnetization hysteresis and modifications to zero field domain structures relative to a standard thermally oxidized Si substrate. The strength and direction of this anisotropy vary with location, indicating its non-uniform nature, and is estimated to be as large as 700 J/m³ for 25 nm thick permalloy films, and decreases with increasing Py thickness. This substrate induced anisotropy is strong enough to modify the domain structures present in patterned magnetic elements and can have significant implications for the development of magnetic devices on aerogel substrates. Results are compared and found to be consistent with micromagnetic modelling of expected domain structures.