Temperature dependence of electron magnetic resonance and magnetization in NiO nanorods

摘要

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 I_0, linewidth ΔH and resonance field H_r) of an observed line due to uncompensated spins are followed for T ≤300 K. The M vs. H and T variations yield a blocking T_B approx= 250 K, above which the data fits modified Langevin function with magnetic moment μ_p approx=1240 μ_B/particle. For the EMR line, I_0 decreases rapidly for T < T_B, and the line broadens and shifts to lower H with lowering T, following the lineshift δH_r = (ΔH)~n with n approx= 2.8. This is close to the value of n = 3 expected for randomly oriented particles.