Effect of interparticle interaction on the magnetic relaxation in NiO nanorods

Temperature variation (5 K-300 K) of the AC magnetic susceptibilities (chi' and chi') at frequency f=0.1, 1, 50, 100, 500, 1000, 2000, 5000, and 10, 000 Hz are reported in 5 nm diameter nanorods of NiO, with and without oleic acid (OA) coating. Using the peak in chi' as the blocking temperature T-B, it is observed that T-B increases with increasing f. The data for the two samples fit the Vogel-Fulcher law: f=f(0) exp[-E-a/k(T-B-T-0)], with f(0)=9.2x10(11) Hz, E-a/k=1085 K, and T-0=165 K (0 K) for the uncoated (coated) particles. This shows that T-0 provides a good measure of the effects of interparticle interactions on magnetic relaxation and that these interactions are essentially eliminated with the OA coating. (C) 2006 American Institute of Physics.