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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
physics and astronomy
Magnetic anomalies in NiO nanoparticles
Journal of Applied Physics, Volume 81, No. 8 PART 2B, Year 1997
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Description
As first noted by Néel, antiferromagnetic nanoparticles could exhibit superparamagnetic relaxation of their spin lattices is well as permanent moments arising from uncompensated surface spins. Several samples of antiferromagnetic NiO nanoparticles with average sizes ranging from 50 to > 800 Å were investigated in the present study. In addition to the inverse dependence on avenge particle size of the susceptibility predicted by Néel. and previously reported, some unusual behavior was observed. Above the blocking temperatures (TB) of the particles, the reversible magnetization could not be fit with a Langevin function that was consistent with the physically reasonable moment representing the uncompensated spins. For the 53 Å diameter particles, both zero-field-cooled (ZFC) and field-cooled (FC) loops below TB exhibit large coercive forces (several kOe) and the loops showed irreversibility up to 50 kOe. In addition, in the FC state below TB the hysteresis loops were strongly shifted. The latter behavior may be due to exchange coupling of the uncompensated spins with the antiferromagnetic core. However, the large coercive forces and high field irreversibility which accompany the shifted loops raise new questions about the nature of the uncompensated spins. The magnetization relaxation of these particles is also discussed. © 1997 American Institute of Physics.
Authors & Co-Authors
Makhlouf, Salah A.
United States, La Jolla
University of California, San Diego
Egypt, Asyut
Faculty of Science
Parker, F. T.
United States, La Jolla
University of California, San Diego
Spada, F. E.
United States, La Jolla
University of California, San Diego
Berkowitz, Ami E.
United States, La Jolla
University of California, San Diego
Statistics
Citations: 295
Authors: 4
Affiliations: 2
Identifiers
Doi:
10.1063/1.364661
ISSN:
00218979
Research Areas
Infectious Diseases