Hierarchical FeNi₃ assemblies with caltrop-like architectures: Synthesis, formation mechanism and magnetic properties

Hierarchical FeNi₃ assemblies with caltrop-like architectures have been successfully synthesized via a facile solution phase chemical route. The morphology evolution process and possible formation mechanism of FeNi ₃ assemblies have been investigated. Magnetic measurements reveal that the coercivity, H_c, of the FeNi₃ assemblies reaches approximately 320 Oe, which is much larger than for spherical particles. The enhancement of the coercivity may be attributed to the large shape anisotropy. The permeability measurements for the FeNi₃/wax composite show that the imaginary, μ′′, part of the permeability possesses a very broad resonance peak in the 100 MHz-10 GHz frequency range. This broadened peak is believed to be due to the peculiar shape anisotropy of the caltrop-like architectures. The results indicate that the as-prepared hierarchical FeNi ₃ assemblies with caltrop-like architectures have the potential to be used as efficient electromagnetic (EM) wave absorbers in the wide microwave frequency range.