Exchange-coupled Hybrid Nanocomposite Magnets
Abstract
Major Goals: The major tasks and objectives of this project include: Modeling analysis of inter-phase interactions in exchange-coupled hybrid magnets; Investigation of interface effect on the inter-phase interactions; Fabrication of hard/hard, hard/semi-hard, hard/hard/soft nanocomposite hybrid magnets; Fabrication of anisotropic bulk hybrid magnets. Accomplishments: We have succeeded in synthesizing a variety of magnetic nanoparticles and nanostructured hybrid and composite systems. Among which we prepared cobalt nanowires with high aspect ratio via a solvothermal chemical process, with a diameter of about 15 nm and a mean length of 200 nm. Based on the shape anisotropy and orientation of the nanowire assemblies, a record high room-temperature coercivity of 12.5 kOe has been measured in Co nanowires which is corresponding to an energy density of >40 MGOe (assuming a 100% mass density). It was observed in our experiments that not only the coercivity, the remanent magnetization of the nanowire sample also increased greatly upon alignment, leading to the remanent magnetization ratio Mr/Ms of 0.92 (in comparison with ~0.5 of un-aligned samples), which is an almost doubled value compared to the randomly aligned system (while the saturation magnetization remained unchanged). Consequently, the squareness of the loop is significantly increased (to 0.78 from ~0.6). This change is a typical Stoner-Wohlfarth behavior of a single-domain particle system upon magnetic alignment. Based on the model, for an ideal single-domain particle system with identical magnetic properties of each particle, the magnetically aligned assemblies will gain coercivity and remanence values twice that of the corresponding randomly oriented system. This sharp behaviour has been rarely observed in actual hard magnetic materials for the reason that identical single-domain particles are difficult to prepare experimentally.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 2017
- Accession Number
- AD1067778
Entities
People
- Ping Liu
Organizations
- University of Texas at Arlington