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