Strong unidirectional anisotropy in mechanically alloyed spinel ferrites

Abstract

Cluster glass and relatively high coercivity at low temperatures were found in disordered ultrafine nickel ferrite powders. High-energy mechanical milling of spinel NiFe2O4 led to formation of a wüstitelike structure. Our investigation suggested that ferrimagnetic clusters formed in an antiferromagnetic matrix. The strong ferri/antiferromagnetic exchange coupling resulted in a strong unidirectional anisotropy and a coercivity of over 10 kOe at 4.2 K. © 2007 American Institute of Physics.