期刊
SOLID STATE COMMUNICATIONS
卷 145, 期 4, 页码 192-196出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ssc.2007.10.026
关键词
magnetic nanoparticles; blocking temperatures; size dependence; electron magnetic resonance
Size dependence of the blocking temperature T-B (determined by SQUID magnetometry) and electron magnetic resonance (EMR) spectra are reported for NiO nanoparticles (NPs) with diameter D = 5-20 nm. Comparison of the T-B vs. D variations in the oleic acid (OA) coated and uncoated NiO NPs is made. The hi-her blocking temperatures observed for the uncoated NPs are suggested to result from the effects of the interparticles interactions (IPI). For the coated NPs with negligible IPI, the expected linear variation of T-B with volume V of the NPs is valid if effective anisotropy constant K-eff increases with decreasing V. The decreasing intensity of the EMR signal with increasing D is suggested to result from the surface Ni2+ spins whose density decreases with increasing D. (c) 2007 Elsevier Ltd. All rights reserved.
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