Temperature dependence of electron magnetic resonance and magnetization in NiO nanorods

For NiO nanorods of 5 nm diameter prepared by sol–gel technique, variations of the magnetization M with temperature T (5–370 K) and magnetic field H up to 55 kOe are reported. Also, temperature variations of the EMR (electron magnetic resonance) parameters (intensity I0, linewidth ΔH and resonance field Hr) of an observed line due to uncompensated spins are followed for T≤300 K. The M vs. H and T variations yield a blocking TB≃250 K, above which the data fits modified Langevin function with magnetic moment μp≃1240 μB/particle. For the EMR line, I0 decreases rapidly for T<TB, and the line broadens and shifts to lower H with lowering T, following the lineshift δHr=(ΔH)n with n≃2.8. This is close to the value of n=3 expected for randomly oriented particles.