Tuning Magnetic Anisotropy from Uniaxial To Easy-Plane Via Composition Gradient in Electrodeposited Co–CoW Nanowires

https://doi.org/10.1007/s10948-025-07102-7

The ability to design magnetic anisotropy in one-dimensional nanostructures is a cornerstone of modern spintronics and data storage. Typically, the high aspect ratio of nanowires dictates a dominant shape anisotropy with an easy axis parallel to their length. Here, we demonstrate a dramatic reversal of this paradigm in composition-gradient Co-CoW nanowires. Using a tailored electrodeposition process, we fabricate nanowires with a smooth transition from crystalline hcp-Co at the base to an amorphous CoW alloy. Structural and elemental analysis confirms the controlled longitudinal gradient. Strikingly, magnetic characterization reveals an easy magnetization plane perpendicular to the nanowire long axis, a direct inversion of the conventional easy-axis orientation observed in homogeneous Co or CoW nanowires. This gradient-induced anisotropy is accompanied by a significant enhancement of transverse coercivity up to 250 Oe. The anisotropy field distribution and first-order reversal curve (FORC) analysis reveal a multiphase magnetic system where the magnetization switching is governed by coherent rotation and localized domain wall motion, driven by internal magnetostatic and magnetoelastic effects originating from the composition gradient. Our findings establish compositional grading as a powerful tool for designing unconventional magnetic anisotropies in functional nanomaterials.