Exchange-Coupling Interaction in Zero- and One-Dimensional Sm₂Co₁₇/FeCo Core–Shell Nanomagnets

Abstract

Rare-earth-based core–shell spring nanomagnets have been intensively studied in the permanent magnet industry. However, the inherent agglomeration characteristics of zero-dimensional (0-D) magnetic nanoparticles are an issue in practical fabrication of magnetic nanocomposites due to deterioration in exchange-coupling interactions, resulting in inferior magnetic performance. Here, with an aim to overcome the structural limitations, we report a new type of SmCo/FeCo core–shell nanomagnet with a well-dispersed one-dimensional (1-D) structure prepared by a combination of electrospinning and electroless plating processes. An FeCo layer with a tailored thickness on nanoscale SmCo was produced to achieve a sufficient exchange-coupling effect. The influence of electroless plating time on the microstructure of fibers was discussed, and comparisons were made as a function of the magnet shape. A 1-D SmCo/FeCo spring nanomagnet having a core diameter ranging from 150 to 200 nm and a shell thickness of 15–20 nm showed a potent exchange-coupling effect compared with its 0-D counterpart. This effectively reduced self-aggregation and further showed a remarkable enhancement in (BH)max (above 45.7%). We think that this novel structure marks a new era in the exchange-spring magnet industry and may overcome the limitations of traditional core–shell nanomagnets.

Extraordinary Magnetic Hardening in Nanowire Assemblies: the Geometry and Proximity Effects

“…An additional approach to increase the energy density is to coat the Co NWs with high saturation magnetization Fe or FeCo alloys, to form the exchange‐coupled core/shell nanocomposite systems. Our preliminary studies on the Co/FeCo core–shell nanowires produced via electroless plating technique [ 58 ] have shown an improvement in the remanence magnetization from 16.6 kG for pristine Co NWs to 19.3 kG upon coating Co NWs with FeCo of volume fraction f = 0.3 (see Figure a).…”

A review on electrospun magnetic nanomaterials: methods, properties and applications

“…In this case, two different spinning solutions are loaded into inner and outer syringes. Each jet flow is then formed with a different velocity and collected before being annealed to obtain magnetic-magnetic, [153][154][155] magneticluminescent 156 or magnetic-electric 48,140,157 bifunctional coreshell nanofibrous materials.…”

“…171 In addition, 1D hard-soft exchange-coupling nanomaterials offer a unique platform for enhancing the maximum magnetic energy product [(BH)max] due to the reduced selfaggregation when compared to their 0D counterparts. 124,154 In another case, Lee et al 154 fabricated core-shell Sm 2 Co 17 /FeCo NFs by electrospinning, calcination, calciothermic reduction and electroless plating. Relative to its 0D counterpart, the well-dispersed 1D/core-shell nanostructure demonstrates an enhancement in (BH)max (46% increase) as a result of the dense homogeneous soft magnetic coating as shown in Fig.…”

“…7 Scheme of expected magnetic performance in a uniform, onedimensional, hard-soft magnetic core-shell nanocomposite and its counterpart. 154 Adapted with permission from ref. 154.…”

Lattice-Match Stabilization and Magnetic Properties of Metastable Epitaxial Permalloy-Disilicide Nanostructures on a Vicinal Si(111) Substrate

“…Further technological progress in the field of magnetic data storage and spintronic applications requires the nanoscale miniaturization of magnetic devices with large remanence and energy production [ 1 , 2 ]. This demand has led researchers to combine magnetically hard and soft phases in bi-component type nanomagnets, to facilitate exchange coupling, in the form of core-shell [ 3 , 4 ], bilayer [ 5 , 6 , 7 ] and nanocomposite [ 8 ] structures. In the absence of exchange coupling in single component nanomagnets, remanent magnetic moment, coercive field, and the shape of the magnetization reversal loop, reflect a single magnetically hard or soft phase.…”