Direct Writing of Shape‐Gradient Magnetic Alloy Microwire Arrays with Meniscus‐Confined Electrodeposition Process

Abstract

recording due to their high aspect ratio, high coercivity, and high storage density. [6] Modulating the magnitude of the coercivity and the saturation magnetization by combining magnetic materials and pure metals was initially developed in 1978 to produce binary and ternary alloys. [7] Since then, binary alloys have attracted widespread attention due to their potential applications in magnetoresistive and thermoelectric devices. [8] In recent years, the influence of morphology [9] and composition [10] inhomogeneity on magnetic alloy micro/nanowires has been studied extensively. But the preparation of ordered gradient micro/nanowires with controllable diameters and compositions is still a major problem.The gradient magnetic anisotropy is so far mainly achieved by changing the material shape of a single metal micro/ nanowire, [11] or by changing the material composition of alloy micro/nanowires. [12] The anodic aluminum oxide (AAO)-templated electrodeposition method [9] is the most commonly used method for mass production of gradient micro/nanowires. Prida et al. [13] employed a SiO 2 -coated hard AAO membrane as the template for electrochemical growth of multisegmented Co-Ni nanowire arrays by alternately varying between two different deposition potentials. Magnetic anisotropy is realized with the prepared wire arrays due to the alternating composition and crystalline structure of the individual segment. To realize shape gradient, Arzuza et al. [14] combined the three-step anodization with an intermediate chemical etching step to modulate the wire diameter.Gradient magnetic micro/nanowire arrays have attracted widespread attention due to their interesting properties. However, fabricating such an ordered array of gradient micro/nanowires with controllable diameters and compositions is still a great challenge to most of the current methods. Here, meniscus-confined electrodeposition (MCED) technique is adopted for the rapid prototyping of the shape-gradient magnetic Cu/Co-alloy microwire arrays by adjusting the printing speed continuously, which provides a novel idea for the preparation and performance research of shape-gradient magnetic alloy microwire arrays with well-defined structures. It is found that the key to fabricating controllable gradient alloy micro/nano structures by increasing the printing speed is to continuously stretch the meniscus within the stable range of the meniscus. In the range of incremental speed in this study, the shape-gradient magnetic alloy wires with stable and uniform compositions and dense internal structures can be successfully prepared, and the gradient ratio can be adjusted from 0 to about 0.025. Compared with the uniform-diameter array, the shape-gradient magnetic alloy array shows an improvement in remanence and coercive force.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admt.202200024.

Magnetic Properties of 2D Nanowire Arrays: Computer Simulations

“…We considered two limiting cases of nanowire orientation. Arrays of nanowires angled to the substrate or having a thickness gradient [51] may exhibit additional supermagnetic ordering phases.…”