Novel NdCo sub(5) nanoflakes and nanoparticles produced by surfactant-assisted high-energy ball milling

• Published in: Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology 2012-02, Vol.14 (2), p.1-6
• Main Authors: Akdogan, Nilay G, Li, Wanfeng, Hadjipanayis, George C
• Format: Article
• Language: English
• Subjects: Anisotropy; Ball milling; Coercive force; Magnetization; Nanocomposites; Nanomaterials; Nanoparticles; Nanostructure
• ISSN: 1388-0764; 1572-896X
• DOI: 10.1007/s11051-012-0719-6

High-energy ball milling has been shown to be a promising method for the fabrication of rare earth-transition metal nanopowders. In this work, NdCo sub(5) nanoflakes and nanoparticles have been produced by a two-stage high-energy ball milling (HEBM), by first using wet HEBM to prepare precursor nanocrystalline powders followed by surfactant-assisted HEBM. NdCo sub(5) flakes have a thickness below 150 nm and an aspect ratio as high as 10 super(2)-10 super(3); the nanoparticles have an average size of 7 nm. Both the nanoparticles and nano-flakes exhibited high coercivities at low temperatures, with values at 50 K of 3 and 3.7 kOe, respectively. The high values of coercivity can be attributed to the large surface anisotropy of nanoparticles that leads to an effective uniaxial-type of behavior in contrast to the planar anisotropy of the bulk samples. Angle-dependent magnetization measurements at different temperatures were used to determine the spin reorientation transitions in the nanopowders and nanoparticles. The nanoparticles showed spin reorientation temperatures, T sub(SR1) = 276 and T sub(SR2) = 237 K which are lower when compared with the values of 290 and 245 K, respectively for bulk.