Magnetic properties of nanorods of NiO (diameter approximate to 5 nm and average aspect ratio approximate to 12), with and without oleic acid coating, are reported. Temperature variations (5 to 300 K) of the magnetization and electron magnetic resonance (EMR) spectra were measured to determine the respective blocking temperatures T-b(m) and T-b(EMR). The following differences are noted: (1) T-b(m) is reduced from 230 K (uncoated) to 85 K (coated) for H=25 Oe (2.5 mT); (2) Decrease of Tb(m) with H is weaker and the ratio T-b(EMR)/T-b(m) is smaller for the uncoated particles. These differences are due to stronger interparticle interaction present in the uncoated particles. (c) 2005 American Institute of Physics.
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