We conducted magnetic study over wurtzite CoO nanocrystals (about 45 nm in size). The blocking temperature TB and Néel temperature TN were confirmed by comprehensive magnetic characterization. Below TB of ∼7 K the nanocrystals exhibit coercivity of 400 Oe and exchange bias of 206 Oe ascribable to composition influences of uncompensated surface spins as well as to antiferromagnetic volume phase. The uncompensated magnetic sublattice and the spatial distribution of the anisotropy axis relative to the magnetic field are proposed to be responsible for the distinct electron spin resonance (ESR) line shape. Based on the temperature dependence of ESR intensity, the accurate TN is found to be 245 K. It is observed that there is anomalous change in resonance field and line width around TN.
Scopus Subject Areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films